i had a guy welded a magnaflow muffler on my wrx a couple months ago, but the stupid guy did a poor job and now it started to leak at where he welded. does this kind of exhaust leak hurt performance a lot? i'm planning to fix it myself. should i weld it or get the hi-temp sealant thing from auto part store? anybody from sf bay area has welding equipment that i can borrow?

 

i would weld it, you should go back to the place that put it on and tell them they did a crappy welding job and make them fix it for free. with welding, its easy to fix a small hole

and its not going to give you any loss in performance