Hello I have a 95 subaru which has gone thru some changes over the last year. It was bought with light front end damage which was fixed, it was FWD and 1.8 engine. I bought it with a wrx drive train and engine and ecu, well taking it 1 step at a time, It first convereted it to AWD and put RS front and rear brakes on it. then the 1.8 engine was just a dog with AWD so we swapped my friends 2.2 engine which he had left over from his 98 impreza since he has a ver6 sti swap in his 98 preza. Well I left the stock 1.8 ecu in and it runs the motor fine except the EGR CEL shows cause the 98 doesnt have the EGR, Well now of latley when it is cold sometimes it will bog out when it is cold. It does it around 2500 to 3500 rpm and it losses all power and I cant tell if it backfires sometimes thru the exhaust or intake but it does backfire. It is all stock intake and exhaust so it is kinda quiet, Now if I put the clutch in it will rev no problem and if I downshift so the RPM's are higher than 4k it will rev no problem. This problem only lasts like 30 secs.

any ideas, I am wondering maybe temp sensor

I am still working on getting the wrx engine in,I am waiting till spring, I am looking for some sti version 6 suspension, email me if you are looking to sell

The problem is probably due to the fact you are running an OBDII engine with an OBDI Ecu, probably. You may be having compatibility issues with EGR and open loop running.

see thats what I would consider, but it ran perfect for 6 months and now is started this stuff,

just about everything is from the 1.8 engine except the block and heads and the 2.2 injectors

Ah, there's the likely problem. It still thinks it has the smaller injectors. Try using an SFC and see if you can fix the problem. If you have access to a dyno, you might even be able to get another 8-10 hp out of the engine that way, even without other bolt ons.