Where do I get this stuff. I keep finding heavy tubing but have not found any of the thin stuff. Thinking about taking my FM3 turbo DP (not currently on the car - might pull my T25/28 and replace it with that), cutting the flanges off, and reusing them on 3" piping vs the 2.25" stuff that is on there now. The FM3 manifold looks like dog poo - not sure who built it but it is pretty bad.

 

i've got an fm3 manifold. my ext wg is capped off. it's an option i'll consider later. the casting i've found to be very good. the mating surfaces for the turbo are a bit oversized, but i'm using a metal gasket there. it might look like poo, but it's stout.

have you tried mcmaster.com for the tubing?

 

The last place I'd use small gauge steel tubing is on the down pipe. Imagine the heat, imagine the lack of strength/durability. 16ga. would be an absolute minimum - or is that what you're talking about? If so- summit, jc whitney, good muffler shop...