RE: DLE 30 Pitts wrap around
Hi Jim,
Not sure I understand the question. I believe you may be referring to the outlet tube on a muffler. If so let me put it this way. That diameter is larger than what we would use on most 150 twins. But it all comes down to muffler design and what you want out of the muffler
As for smoke on a gas engine it depends on how much oil and the way its being dumping into the muffler. You would probably get better smoke with a smaller outlet as it would hold the heat of the exhaust in a little longer.
Al