Wont accelerate under boost, misfires, backfires, and wont idle

[Andrew - turbo a]

Ah, where do i start? First time poster here, but i've searched for the right answer to my problem for hours on these forums.

I bought an 88 supra turbo a, one of 500 from japan, imported into australia. When i bought it, three weeks ago, it had a blown head gasket

So, i stripped it down, and did the head, put it back together, and now it wont run right. It doesnt idle well, it runs rough, and when i take it for a quick drive, it goes fine, until the turbo starts to spool up and make boost. Just under the point it goes from vacuum to boost, it starts coughing and spluttering, like its hitting a wall, yet if i back off, the boost comes down, and it starts to accelerate. Its quite lumpy to drive, and not at all what it should be.

Now, upon reading the forums, ive heard that it sounds like a large boost leak, possibly causing over fueling, but i cant seem to find any decent leaks anywhere? All the boost hoses are still connected, bit makes no difference. I did a diagnostic test, and it threw up error 52, open circuit through the knock sensor. I'd actually forgotten to plug it in. so i plugged that back up. I also found id missed the vacuum hose from the power steering switch, so connected that also.

I have no idea where to go from here?
Someone else with similar problems disconnected the tps, so i tried that, made no difference at all. I reset the timing, no difference. its got brand new plugs in it, same as what it should have, but with copper electrodes as i couldnt get new platinum ones today, so ill put the correct plugs in when i can get them. the new plugs did make a difference, but its still not right.

What else can i do!

[Andrew - turbo a]

Well, as it turns out, looks like my map sensor was disconnected

As its a turbo - a, it doesnt have a maf sensor, it has a map sensor instead, and it appears when it doesnt recieve a signal, it overfuels