Had this issue for quite some time now; seems to be more prominent with the CAI - and during cold mornings.

I'm relatively sure it's the car hitting boost cut (or fuel cut? I do have a walbro fuelpump and yellowtop injectors to my belief) as my mechanical boost controller spikes a hell-of-alot during cold mornings/nights - but the problem I have seems to diminish during slightly warmer weather.

What tends to happen (and moreso when hitting full boost in 3rd gear than any other gear) is the motor seems not to be attaining ample fuel/air; causing a subtle jerk and feels asif it's trying to make riddance of perhaps unburnt fuel out the exhaust. You'll find that some backfiring occurs, accompanied by a popping sound that generally comes from the vicinity of the exhaust. Perhaps it's a detonation issue. I'm really not sure.

I've tried turning down my boost, but it makes the turbo laggy as hell - so i'm thinking of re-attaching it to the stock boost solenoid, because I'm sick of trying to pull in any gears - and it honestly feels asif the spark is being retarded. Maybe it's an ignition issue? I am absolutely perplexed.

I'm running no BOV so perhaps turbulent air recirculating upon the closure of the throttle body is playing games with my AFM. I might get some contact cleaner to the AFM this weekend and see if it changes anything.

Any enlightenment would be appreciated, as it's really got me scratching my head!

Cheers.

__________________
03 STi @ 280hp/1.3bar

What ECU?
How much boost (yes I see 13 psi in your sig)?
When were the plugs last changed?

__________________
[CENTER][SIGPIC][/SIGPIC][/CENTER]
[CENTER][COLOR=#ff0000]Built Ej207: Semi-closed RA Cases - Wiseco Forgies - Manley rods - BC 272 cams - GDA Heads - billet f/whl - Vi-pec - WbO2 - 800cc Yellow tops - TD05-20G - 409Hp ath @ 1.75bar on E85[/COLOR][/CENTER]

Check your plugs.

Are you still running original RS ignition coils? Because by this age, they fucking suck ass.

__________________
RS Liberty - Because WRX's are only good for parts...

You have allready listed the first half dozen things to check.
Not sure about subies but my experience with boost cut is it is not subtle.

Check the colour of your plugs, clean them. Leads and coils may be at fault also.
Remove mech boost controller. Back to stock.
Hit your MAF with some contact cleaner.
Check all intake fittings are tight and no splits.

All the basics.

You should really concentrate on the road rather than jerking it when on boost

__________________
[COLOR="Gray"]550Nm off a 2L... Just wish it was in the dak dak...[/COLOR]

haha it's exactly what i was going to say!

__________________
Member of the 18-35 club and proud of it! (For another 5 years...getting old)

New toy has arrived, 1/4 mile in 11.2 sec and only 114hp!

My mind was with Kato's...

MBC is set to 11psi (AFRs were fine when it was dyno'ed at this boost pressure although it did begin to lean out top-end at 13psi), but it creeps during cold weather, as colder air is far denser. ECU is stock from a JDM 1997 GT-B Touring Wagon. Motor is a JDM EJ20H from that car too.

I haven't changed the plugs since I've owned the car. So I think that'll be on my to-do list. From your individual experiences; are there any specifc plugs you guys would recommend? And what is the optimum for them to be gapped to?

Coils are situated directly above the sparkplugs, rather than a coilpack atop the manifold. So they're not standard AUDM issue, nor is the motor from a g1 RS.

__________________
03 STi @ 280hp/1.3bar

It's unlikely to be the coils then, as the coilpacks on plug are quite good. Try new plugs, NGK Platinums - Maybe a tiny bit smaller the OEM recommendation?

Clean your AFM as mentioned - What is your boost cut set to? I reckon your stock ECU is just hitting boost cut.

__________________
[SIGPIC][/SIGPIC]
Should have bought an STI

Not sure. To my belief 15psi. And I think it definately creeps up there some nights when it's shitfully cold.

Only does it intermittently. The car will feel asif it's halting a bit; and then you'll find the boost will settle and the car will continue to pull with ease.

__________________
03 STi @ 280hp/1.3bar