sounds like it needs a MAF relocation. or possibly bpv issues
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maf relocation is never a solution, it is an upgrade....however, this isn't going to fix his problems here and in a few cases this will actually cause problems on some msps
the others here have some good points, such as the fuel pump dying out or the vacuum lines...have you checked your wastegate to make sure it is still good?
take the vacuum line leading to the wastegate and blow into it, it shouldn't let any air pass through...if it does, there is your problem....a lot of people dont realize this as an issue until its really bad because the symptoms can be really weird until that point
Id also spray some maf sensor cleaner on the maf sensor
if that doesn't help, get a boost gauge and check your vacuum levels, you should be reading 20ish inHg of vacuum at idle, and around 21-22 after you take the car out of gear and the rpms are falling...if not then you have a vacuum leak
as for mentioning injectors, you cannot run larger injectors on this car on the stock computer....you have to run either a piggy back or a standalone....as for running a gt28 on this motor, I wouldn't run more than 10 psi on it, however that is pushing it still...Ive seen these motors blow even when stock, running a larger turbo on stock internals has been done a lot but it is still risky
that being said, congrats on the car!