I have swapped the engine in my 90 civic with one out of a 96. It seems to run great but I am still using the intake manifold off the 90s engine and would like to switch to the one off the 96 engine.
Are there any differences in the electrical\vacuum houses. The 1990 was a single injector setup and the 1996 is a multi point injector setup.

It recently failed emissions tests so I was hoping that this would help it pass.

Oh also it is running the dizy off the 90 engine on the 96 engine. Is this going to have the correct curve for this engine?

Anything else besides plugs\wires\timing that you can think of to help me pass the test for only 2 more years.

 

Converting from DPFI (1990 system with throttle body injection) to MPFI (one injector for each cylinder) is well known as many people have done it. You will need to install a MPFI ECU with matching distributor. The DPFI distributors lack a CYL1 sensor which is necessary to synchronize the MPFI process.

Also a considerable amount of rewiring. Most people prefer to fit the 1992 to 1995 OBD1 system since it is simpler than the OBDII system introduced in 1996. There were also MPFI OBD0's in the pre 1992 Si model.

Swapping on parts from a newer car is generally legal (and likely to reduce emissions) but you may run afoul of California's strict laws if you live there.

How did it fail? If your cat is bad for example the only cure is to replace it.

 

Had double the amount of nox and co2.
I would like to go the ODBII route just to have the better trouble codes than this one puts out.