I swapped a b16a motor into my 90 CRX, and it seemed to run great for a while, BUT, now it stumbles or bogs coming off part throttle. I changed the fuel filter, it is not throwing any error codes (After I fixed the TPS), but gets real bad mileage. It seems to run butter when its cold. The spark plugs, when I pull them out and look at them are white, although it feels like they are fouled when coming off part throttle. It runs good at full throttle. Timing is on the red mark, but I have tried it advanced from there without any change. I did not change the timing belt when I swapped the motor but did take it off and put it back on (I couldn't find a correct replacement).
Stumbling cures???