could be an air leak, check all your connections from MAF to throttle body and all vac hoses. If nothing, then I'd try some STP gas treatment, which will take out the water out of the gas. Those are your most likely culprits

 

The rear bank might be starved a little. Try the fuel filter and if that doesn't work take off the tiny stock fuel rail loop on the tranny side of the fuel rails and check it to make sure nothing is clogging it. That is of course if it's not something simpler.

 

That was my first thought as well. A leak under high vacuum could cause the wastegate to stay open, when you ease up the leak lessens or stops and allows it to close.

With the age of the car and the underhood heat from 2 turbos it might be a good idea to replace your vacuum lines if it has never been done before.

 

this. cheapest first. and if its clogged it will cause all of what you said. my fb rx7 would run fine under half throttle, but as soon as i went half throttle to WOT, it fell on its face. to the point where it wouldnt even run. replaced a bunch of shit and i still couldnt figure it out. turned out, it was the fuel filter the entire time.

always replace the cheapest stuff first.

 

try fuel filter, or it could be fuel pump. get a fuel pressure gauge and see what the psi is.

 

Sorry forgot to mention the car is N/A lol

Thanks for all the suggestions guys. I have off tomorrow so I'll let you know what I find.

 

Shit didnt know you had a 3kgt

That's what my roommate has lol

we just pulled the wire's off the coilpack and tested it that way
saw that number 5 was getting inconsistent spark

Try this and if it is bad go to advanced they were the cheapest around

hope it works out

 

Check the fuel pressure, its the easiest way you can make sure everything from the pump to the filter and regulator are working correctly. If you are careful you can even do it with a tire pressure gauge on the test port.

If that's good then start looking for plumbing leaks. If there are none then it could also be a bad MAF or MAP sensor as well.

 

I dont know a whole lot about 6G72s, but does it have a variable TPS? It sounds like that being out of calibration or dead is also a possibility. I also am not sure how dependent the ECU is on the TPS, but in some Japanese cars like mine, it practically doesnt care if it's plugged in or not. The only differences you'll notice are worse MPGs and the problem youve described.

 

How old are the spark plugs/wires/fuel filter? Any vacuum leaks? I would try regular maintenance items first such as those.