sorry to be picky, but i think the idle is at 750, not 500. i think once you put the stock bpv on, all your problems will be gone. i used to backfire with my HKS and I die out coming out of my driveway a lot. I'm boosting 1.3 bar on the stock one with AP Stg 2 and it's holding up fine.

 

my HKS is fine with me...

it drives like i have the stock one on... it's just louder...

 

maybe your recirculating plug came out...

 

ok my bov was staying open when i reved it. thats why it was dying on me...last night put in about 4 washers and it seems to be running ok so far...idles at 750-500 rpms,sometimes drops to about 400 but its not as bad as no washers where it used to drop down to 300-100 rpms that was ****ed... maybe one more washer would do fine...
it sounds alot more sharper and shorter now but its still good =)