hi im a newbie on the site so sorry if i ask a daft question or 2! haha
i have a 2001 wrx estate on 60'000 on the clock- when i got this car i new it had a fault- i had a code reader which said the lambda sensor was fooked. basically it drank fuel and didn't perform at all as it was in limp mode- wouldn't go past 3500rpm.
i replaced it yesterday with a new denso sensor- reset the ecu and had the fault codes erased. now the only thing thats changed is that is goes well upto 4rpm then missfires, it basically struggles when the turbo boosts. when i come to a stop and the revs drop to idle the oil pressure light comes on- it goes out as soon as i rev the engine. there is no smoke out the back at all. the turbo spins nicely
a few things about the car:
the car has a after market dump valve on it meaning one of the pipes has a bung in it
it has a hks cone air filter apart from that its standard- i think.

can anyone shed some light on this im thinking its either:

1. spark plugs/coils are burned out due to the lambda sensor playing up
2. dump valve/ cone filter combo is messing around with the turbo
3. split in pipe etc or
4. something bad- i really hope not


any help will be great as this is my first impreza so im new to these engine designs etc- im hoping its something simple since there is no nasty smoke out the back and the miles is pretty lowish? anyone had this problem before?

 

id be wary off the oil light my rs turbo did this and it was bottom end sounds like maf sensor

 

i know what u mean although the light is only on when the idle is playing up

 

Has it been remapped for the cone filter and dump valve?

If it hasn't I'd start by replacing them with the standard items as they may be playing havoc with your air intake readings

 

is there any way of knowing its been remapped?