Eh...., that collector is bad. The welds on the collector are not consistant they seem to get large then small. Also your not susposed to run a continious weld on stainless it dosent look good and causes it to be brittle due to the heat. What amperage are you welding with? Also looks like you have some sugar inside your collector, not good. On runner #1 it also looks like you have a cavity on the 3rd weld from the flange (hard to tell from pics), where the pipe meets the flange it also looks like undercut. You realy should have cleaned the metal before welding it i.e wire wheel/laq, it would have came out alot nicer and easier to weld on. I see those welds cracking over time but only time will tell. I would realy like to see power numbers once this is finished however, interested to see how that collector effects your powerband.