My 94 DC2 is straight pipe. DC 4-1 headers which is 2.25 in, piping which is 2.5 in, and 5 zigen muffler which is 2.25in... it sounds too loud and i was wondering should i get a 2.5in muffler ( what kind ) or should i change my piping to 2.25in and get a resonator. and do i lose power for going 2.5 inch piping on an LS.

 

do a search regarding back pressure

 

Get a resonator or two on your setup. BTW, why did you decide to get 2.5 inch piping even though your header and muffler was 2.25?

 

throw on a glasspack

 

I say if your header is 2.25", go with 2.25" exhaust piping. Yes, throw on one or two resonators to quite the beast down.
You don't want to attract too much attention to your illegal exhaust setup. Make sure to use a flexpipe too. Don't want to many clicks and clanks.