I just bought a 92 prelude with the h23a1 engine. It had lost a head gasket and the lady that drove it severely overheated it. I have replaced pistons, bearings, etc. Now that I have it back together, it will start and idle in neutral or park, but once it's put in gear it runs extremely rough. If I try to move it, it will backfire back through the intake. One time it blew the air filter housing apart. I have checked my cam timing, and it seems okay. I get no codes from the check engine light when I jump the diagnostic connector. By the way, no modifications, yet. Any ideas, I'm running out of patience.