Upgraded MAF sensor?
 

I was wondering if I got the Lexus MAF sensor (that alows you to use 550 injectors with the stock ECM) do i have to have the car tuned so it does not run like hell? I'm just wondering cuz my stock MAF shit the bed today and I don't see the point in buying a new stock one cuz down the road I was planning on upgrading it anyway.

You don`t, but if you can, it would be better if you tunned your car.
There are someoptions out there to replace the stock MAF, and you should consider them especialy if you are planning to incease boost past 1,7 barr, or if you are going to buy an EMS for your car in the future.

And where can i get a lexus afm new or used at a decent price?

There are several threads with sites where you can buy upgrade parts.
Me, I am buying all my stuff from www.horsepowerfreaks.com