Ive got a 91 lude si... I put the b20a5 in it cause the b21 was knocking and such... when i drive the car, it runs perfect until the engine warms up to the middle... when it gets there it starts bogging or a hesistation up to around 4k... Ive changed the spark plugs, wires, dist cap, rotor button, fuel filter, and none of this has helped... any suggestions?

 

Check your plugs are they covered in gas? Take out your plugs and let the spark plug holes air out. That worked for me because my spark plugs were covered in gas.. I had the same exact problem you had too.

 

Check your catalytic converter. It may be plugged, or your 02 sensor. A bad 02 sensor will cause you to run too lean or rich I cannot remember.

 

what do you mean by plugged?

 

i had a similar problem and the heat is questionable but check all of you injector clips and possibly swap out injectors if its not the clips. Theres only so many things that can cause a bog and youve pretty much nailed them, ecu can do this as well.