R33 backfire

[tristan]

My Series II R33 GTS25T has been tuned twice in the last 6 months (last time by CRD in Sydney) and continues to backfire (pop) on shifts of medium to high load.

Mods are:

K&N Pod filter (but previous high perf HKS airbox did it too)

Upped boost (standard turbo)

Std ECU and AFM

3" dump pipe

Hi Flow cat

Hi-flow 3.5" exhaust

Platinum plugs

All else stock.

However from memory did not do this before fitment of dump pipe and larger cat.

Methinks backfire is caused by unburnt fuel... maybe mix is too rich or exhaust flow too high for std setup.

This has got me stumped. Just want to make sure that am not harming anything mechanical.

ALSO, since fitting pod filter - there is noticeble lag/hesitation at around 2500-3000 rpm before turbo kicks in. Would fitting Pod filter upset state of tune?

Any help greatly appreciated.

[R31Nismoid]

what BOV you running?

and there wouldnt be much "tuning" going on with a stock ECU mate. Hope you aint paying out the ass for it cause you cant tune a stock 33 ECU.

[Robo's]

Yes it would be unburnt fuel, the standard computer runs very rich once you start turning the boost up.