pretty much done with my 4g63/colt swap. Right now my car is running cat-out. I've got new plugs and wires but the engine misses, engine smooths out as rpm's go up, but is the missing causes by the lack of backpressure? What size pipe should i get and any muffler suggestions?

 

Your car will not "miss" because of loss of "backpressure". Backpressure is not wanted in any car, NA or forced induction. It is all about the exhaust pulses. If your piping is too big while running a low power NA car, you will not have enough pulses to fill the exhaust chambers and you will notice a loss in torque. If you have the right size piping for your motor, each pulse will help pull the next pulse through causing the exhaust to exit faster and more efficient.

Your car is missing due to your ignition. Check your coil pack, what are your plugs gapped to. If you are staying stock on a NA 4g63, then I wouldnt go any bigger then 2.25" or so. If you plan to do some heavy NA mods or a small turbo setup 2.5" would do you better.

 

plugs are gapped to .044 and i've tried another coil and it does the same thing. think maby my injectors are clogged??? or timing off a tooth??

 

Hard to say, do you have a logger? Check and see where the CAS is positioned. Not sure on NA cars, but that seems like a big gap. The 4g63t likes plugs gapped to .028-.032

 

yea N/A motors are supposed to be gapped to .044 but i think my fuel filter/injectors are clogged cause i drove it this morning and when i get on it, its goes for a bit, (no tach) but higher rpms maby like 4500-5000 it dies and a buddy said sounds like detonation =(. and i already replaced the fuel pump and it doing the same thing

 

May as well replace the fuel filter, they are cheap. Try some fuel injector cleaner as well.

Check your plugs, what do they look like? Your plugs will tell you a lot about what is going wrong.