im buying a universal muffler, most likely a magnaflow..now, the stock piping on my hatch is 1.75", but i plan later on going 2.5" full back later..question is, will a 2.5" inlet weld alright to the 1.75" stock pipe? or should i buy the 2.25" inlet? or will i have to go down to 2.0"??? thanx

 

come now, dont be shy...

 

Get the mufler inlet at the later planned system o.d. I believe 2.25 is a good all-around diameter. Search and learn. But keep the sacrificial downsizing at the main unions.
Example - axle back for now should be one size. (2.25) Don't get a muffler with a weenie inlet and have to neck down your tailpipe later to accomodate it. It wouldn't cost much at all to have them re-use your flange at the rear axle area and run the 2.25 back to your muff. It's till a little restrictive, welding the 2.25 to a smaller flange, but it's alot better than the other way. Then , later, the system will match. Also, the larger muffler will sound better. Someone recommended 2.5 cat-to-axle, 2.25 on out to muffler. 2.5 is a big-*** tube for a non-turbo system.