Mig can throw a bunch of spatter, if not properly set, speed, etc. I`m narrowing one and the perch welds were super hot,run fast, and left 1/2" or so gouges at the ends of each weld. nasty but served the purpose, houseing looked better but gobs of spatter shallow concave weld, but served its purpose. The ring for the center section, looked good, more critical. housing ends, real critical, smooth and could`nt tell if it was welded,has to be with some process, I haven`t seen. If housing ends were arc welded, the houseing was probably narrowed. good luck resolveing the issue.