Impreza sti 06 jerking, hesitation and loss of power

[Perkyp]

Hi guys

I have owned my impreza sti since december last year without performance issues. A couple of weeks ago the eml came on for front o2 sensor. After checking and clearing the code I now have jerking and hesitation around 10psi and a large loss of power but then goes to 20psi but  feels shakey and still low power. Both sensors were changed and still the same but no eml. Spark plugs were inspected and show alot of white on the tips, they are only 3k miles old. Compression shows 135 on all 4 cylinders. I found a hole in the turbo inlet hose which I changed for a mishimoto silicone hose. Still having same issues along with overheating after a long run. Head gasket test was done and did not change colour. Vaccuum is stable at just over 20inHg. It has a decat exhaust, and valve delete and should be hittin around 350bhp. Please can someone help with this we are running out of ideas and I have searched everything!

[stants]

Have you reset the ecu ?
Best thing would be to get it on a dyno and see what's going on weather it's a fueling issue or something else, I presume it running a bit lean if the plug tips are fairly white ?

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[Perkyp]

Thanks for the reply. Yep have reset the ecu.

A strange thing with the plugs is that when I purchased the car it had just been serviced and ran perfectly fine until the next service. When pulling out the plugs they were the shorter plugs for the 2.0 engine which was odd. I checked a few specialists which explained they should be the long reach plugs for the 2.5l so put them in and they came out white after 3k.

I have tried the short reach again but same problem still persists. When the short plugs were removed they were no where near as white after 5k miles. I believe this is a seperate issue unrelated to the problem now but still confused by the plug choice.

I have found a video which shows an exact copy of my issue which is coil packs, so that is the next test.

Any feedback for the plugs also will be greatly appreciated

[Wolfy]

This is interesting. I have a similar issue. Sometimes, I lose all power as the turbo spools; I get major backfire then all the boost hits at once. It's quite thrilling, to be honest, but obviously isn't normal.

For some reason my car hates V-power, despite the fact it was mapped on that, it just prefers 97 Ron from Esso and only from Esso. 

 

[Perkyp]

1 hour ago, Wolfy said:

This is interesting. I have a similar issue. Sometimes, I lose all power as the turbo spools; I get major backfire then all the boost hits at once. It's quite thrilling, to be honest, but obviously isn't normal.

For some reason my car hates V-power, despite the fact it was mapped on that, it just prefers 97 Ron from Esso and only from Esso. 

 

It turned out to be a failing maf sensor which didnt throw any codes and 2 small boost leaks!