I have an 89 DX hatch that I bought for really cheap. The number 3 cylinder was shot and so was the headgasket. I swapped in a 2000 D16Y7 longblock from a Civic LX (18K so it's almost new). I used a 90 CRX Si PM6 ecu, PM6 distributor, rewired for MPFI and used a 94 EX intake manifold. I am using the 00 LX injectors without a resistor box for the time being until I get some non-OBD injectors and clips. For an air intake I'm using a stock 99 GSR air tube and filter just for testing purposes.
When I start up the motor it will rev to about 2K then drop to about 500 then back up. It does this for a while then will finally idle at about 800-1K. The exhaust smells rich and the fumes burn your eyes after a while but the timing is near dead on stock to a 90-91 CRX Si. Every now and then the rpm's will drop and the motor bogs and it sounds like it's struggling for air at idle.
I sat under the hood and would gradually open the throttle and it will start bogging then jump up suddenly. A few times there was a loud pop that came out the intake so I would shut it off. I have no check engine lights at this point. I did at first for the cylinder sensor but I had a pin wrong and fixed that. I have no clue as to what's wrong so if someone can help me out with the troubleshooting I'd greatly appreciate it.

 

Bump

 

you need non-OBD injectors and the regulator, that should fix your problem