No high rpm?
 

I have a problem with my 87 supra that was a na body with a jdm 7mgte installed. For some reason the motor just does not like to rev pass 5,000 rpm, it's just not pulling anymore. I suspect either a bad ecu, or a ignitor. It does it under load and also in neutral(its a 5 speed). I did basically bought everything on ebay to convert it to turbo. The coils ohmed out ok. The afm is ok because I hit fuel cut once and the fuel cut works off the afm. I know for sure I don't have a boost leak. I installed a FCD, I currently running 11 psi.

Check codes!! it is probably a plugged cat though. check that out. Take your oxygen sensor out and drive around and see if its any better.

I have no codes, no cat and why would the oxygen sensor cause anything if the ecu ignores the o2 sensor under wide open throttle.

Check your plugs, fuel filter and fuel pump.

X2, especially the filter / pump.

if it isn't any of the above possibly the knock sensor that caused power loss and caused my car to run funny before. could be a long shot though. good luck

If you have a clogged cat and you take the o2 sensor out it gives the exhaust an extra place to go. But since you have no cat you can rule out that idea lol. Also check the above mentioned, boost leaks, plugs, wires, air filter, etc. Make a video of the problem if you can. Does the car miss? sputter or shake? or does it just stop revving up like if you dont open the throttle all the way?

I checked all the plugs, coil packs, wires it's all good. It does not miss, it just stops pulling after 5,000 rpm. It does matter whether the motor is in boost or not, it does it also in neutral so that rules out alot of stuff such as ignition wise being faulty or weak. I'm suspecting either an rpm input such as a cps where data at higher speeds is getting corrupted before it inputs to the ecm or the ecm itself being faulty. It seems engine speed input is the source of the problem.