[429mustang]

I'm gonna weld up my exhaust when I get everything (BBK Longtubes, Dr. Gas 3"- 2 1/2" X-pipe, Spintech Prostreets/Turndowns). I'll be using my friends Lincoln Weldpack 100 wirefeed welder. We've used it for exhaust a few times but couldn't get it to leave a clean/solid weld. There were small holes and the welds were sloppy, any advice on what heatsettings/wire to use? We were using the flux core wire that came with the welder and the pipes wee clean, should we use non-flux wire or try gas shielding? Any info is appreciated, I don't want to trash out my exhaust but I don't want to bring it anywhere and have someone else do a half-*ssed job for a good amount of money.