SR20 Backfire on Accel

[Zeph240sx]

Hi i have an SR20DET RedTop that recently i put on a GT2560R on it. So far im running 370CC and a stock tune on 13psi.

I have some sort of Boost cut or Backfire/afterfire @ 4000Rpm under heavy boost, but if i partial throttle the boost into higher Rpm range i say it is somewhat ok. when in boost the AFR reads around 10.5 ~ 11
Under 4000rpm with heavy boosting i have no problem.

So far i:

New Spark plug BKR7E
Fuel Filter
Cleaned Maf
Cleaned Air filter
Checked Coilpacks
New O2 Sensor

I'm lost to what it is. If someone could help me that would be awesome

[PapaSmurf2k3]

I'd check for a boost leak, and are you running any engine management? How do your plugs look? What are they gapped to?

[Zeph240sx]

papasmurf my plug looks good tanish brown.

I have come to a conclusion that it is not boost issue because when i free rev on no load it bogs around 4800RPM but the idle is fine @ 850RPM No rough idle no nothing

I believe it is Ignition Breakup I checked the coilpacks it doesnt look like it has any cracks. im lost on what to do!!!
some1 gimme da light