i have magnoflow cat and my check engine lite keeps coming on. got it look look at. mechanic said there is to much flow going into and the computer doesnt know how to read it. what ever he meant by that. what should i do wit. i also have a 21/4 piping exhaust done to it. should i replace the hole thing or what

 

find out what code does it throw first, it's most likey is a cel for your new cat.
obd2 honda are known to be picky on aftermarket cat, with straight/test pipe you have no change of getting it away, even some of the performance cat will not do the trick for the ecu.

but i do know randomtech's cat will not throw a code but i not sure if you want to spend some more cash or not.

 

if it is your cat tripping a code, just get a dummy plug to trick the computer.