would appreciate some well known guidance to help upgrade my bone stock '97 MKIV auto

[pwpanas]

Originally Posted by jzzrs180

...Somehow that still screams twins to me..!...

The stock twins do spool up fast, but only because 1) they're small and 2) because they operate sequentially. Read more about it here:
http://www.mkiv.com/specifications/ncf/ncf93/ncf088.jpg
http://www.mkiv.com/specifications/ncf/ncf93/ncf089.jpg
http://www.mkiv.com/specifications/ncf/ncf93/ncf086.jpg
etc...

Originally Posted by jzzrs180

...And I heard you can achieve these goals in the 700's still when talking horsepower....

No, the stock twins can't produce 700rwhp. Whomever told you that is 'smoking crack'. If you're talking about aftermarket twins that run in parallel, then sure 800rwhp+ is no problem, but it'll lag just like a big 800rwhp+ single turbo.

Originally Posted by jzzrs180

...With road racing upgrades where does that get me in top speed, because I do miss 155mph!...

The oem Mkiv Turbo is electronically limited to 155mph. With a US-spec Mkiv Supra Turbo, removing that electronic limitation is as easy as pulling the trac fuse.

Originally Posted by jzzrs180

...LOL used to have a street bike..ha, and boy did I test that thing...

Bikes are about as aerodynamic as a brick at 150mph+. You'll find an upgraded Supra exceeding that easily because of the much lower drag coefficient.

Originally Posted by jzzrs180

...Anyway, I read that the oem auto tran can handle up to 500hp and no more, true?...

Depends, but I'd say about 525rwhp reliably. There are upgrades available that will take you to about 675rwhp with the oem TT auto, but to go past that you'll need to swap it out for a TH400 or the like.

Originally Posted by jzzrs180

...Also I read that all systems are controlled by an integrated engine management system (ems), consisting of a main engine control module (ecm) and several peripheral electronic control units (ecu) for the ancillary systems. How does the obdII play into that system, and if I were to upgrade to a AEM ems, how does that work with the rest of the system, i.e. ecu, ecm?...

An AEM ems works fine with ODBI. With ODBII it's a bit trickier - I've heard of some folks leaving the oem ecu in there for emissions, and using the AEM to control the engine.

Originally Posted by jzzrs180

...1.can you explain how and where do I get this mixture of higher octane fuel...

Everything you saw in that wikipedia article is accurate.

Originally Posted by jzzrs180

..., and is it stored in the main fuel cell together?...

Sure. Either that, or you can inject it separately. Your choice.

Originally Posted by jzzrs180

...What is that ratio?...

Depends how much boost you want to run.

Originally Posted by jzzrs180

...why is the exhaust gear more important to adjust...

um, because that's what you need to do to increase the peak hp at higher rpms? The information we've accumulated over the years in this community is thanks to dozens of early pioneers that experimented with the Mkiv Supra Turbo in the mid '90s. Lots of things were tried, and only some worked. The ones that worked were published so it's easy for the rest of us to take advantage of. Again, here's the link:
http://www.mkiv.com/techarticles/cam_gear/install/index.html

Originally Posted by jzzrs180

...Complete upgraded coolant and fuel systems past 500hp,...

No, only the fuel system.

Originally Posted by jzzrs180

...but with lower horses I'm ok with oem? flex fuel mix (85)?...

No, again it depends on boost. More boost, more octane. Forget hp.

Originally Posted by jzzrs180

...Say I make a bpu where I maintain about 15psi for now, where does the equate in relation to hp?...

I'd guess about 350rwhp max through a 6spd. Possibly 325rwhp-ish through an auto.

Originally Posted by jzzrs180

...Pros n cons of single turbo and/or twins?...

Do you mean stock (sequential) twins, or aftermarket parallel twins?

[pwpanas]

Originally Posted by jzzrs180

I hear ya! The targa model ironically weighs a little more too lol, but that's no real matter, definitely would help me make that decision a little easier.. The only real doubt i have though is telling myself that I just put down over $20k on a car that has just under 90,000 miles, and being ok with it.. If I'm patient, I can justify waiting longer, saving up and putting $30k down for one that has 30-40,000 miles, which would make me feel like I'm still buying a new car..But that's where I'm torn, it does look in great shape and it is a good price for the TT..sooo are the miles really that big a deal!? it's an 7 hour drive north if I wanna check it out..

For a '94, 89K miles is LOW. I've seen more than one well-maintained Mkiv Supra Turbo go single-turbo at higher mileage than that, and put out 700rwhp reliably with no issues whatsoever.

That car won't be around long. If it's still available, put cash (not a check!) in a briefcase, get on a plane, and buy it if it checks out. You may already be far too late if it's legit.

Oh, and a hard-top is more desireable: it's more rare, and as you said the lower curb weight makes it a better (GT) sportscar.

Best case, find a local Mkiv Supra Turbo owner that can take it for a test-drive. That way, you'll have an objective, well-informed opinion about the performance, handling, and all of the specific the sounds it makes during the test drive (turbos, transmission, etc.). If possible, find a local shop with extensive Mkiv Supra Turbo experience, and pay them to give it a complete once-over. At the very least, pay your choice of a local Toyota dealership to check it out. It's critical that you get an qualified, objective third party to provide input.