I've searched the threads but no luck,
My car is an 02 wrx cobb stage 2, up pipe, full 3" exhaust, k&n drop in, 150,000 kms, 93205 miles.
here's my problem, If I'm in neutral and I step on the loud pedal, it bogs down, then it excels and then runs fine. just from idling. Not from 3000 rpm and up.

I replaced the fuel filter last year, my air filter is clean and so is my MAF sensor.
It' not throwing a code yet.
I've heard that it could be: my trubo (stock), fuel filter, or fuel pump.
Last time I looked at the turbo while this was going on, it was fine no oil leaks.
Is there a way to test the fuel pump?
Thanks