i just bought an ES Tuning muffler w/a 2.25" inlet, but my stock exhaust is 2". would it be better to get new pipes, or could i just have my local muffler shop weld up the new muffler?

 

I dont see why you would need a new exhaust kit for that. Although, you probably will not see any type of performance gains if only a muffler is put on. I think a local muffler shop etc. would be able to weld on a 2''-2.25'' adaptor. Not sure how much it would be though.