1988 Crx Si check engine light help.
 

Ok, I have a 1988 CRX Si thats throwing a code 1 light. I just recently rebuilt and replaced the D16a6 in it using the motor and tranny from a 1991 Civic Si. Ive tried two different o2 sensors both new, a different ECU, two separate exhaust manifolds (DC Sports and Pace Setter). I thought that maybe the o2 sensor wasn't getting hot enough when it was relocated to the b pipe (DC Sports) since its not heated and wasn't working properly so I switched to the Pace Setter which has a closer o2 sensor location (more like stock).

I've double checked all the parts to make sure they are correct for a CRX and have searched the web for solutions. The motor isn't running rough, very smooth and the fuel pressure is correct according to Honda so i don't think its a fuel pump or injector issue. The only thing is it appears to be running rich because I'm getting horrible gas millage.

Any ideas/solutions? Any feedback would be great. Thanks in advance!