I'm changing my exhaust system from stock to a performance exhaust. I want to use Tri-Y headers, a Dr Gas x-pipe and Spintech or Flowmaster mufflers (haven't decided which yet). From what I've read and seen here and on the Dr Gas site, their x-pipes are universal and have to be welded together. Can I test fit them, mark them, and then take them to the muffler shop to be welded? Or does the shop have to fit them? I'd like to do the install myself, but I want them to fit right. How did you guys do yours? Also, is 2 1/2 the right size system? It's just a stock K-Code 289 right now but I'm also adding a Shelby-style hi-rise aluminum manifold and a Holley 650.