I have a new Jet Cat P80, and it has a problem at idle. The problem - a "pop" every 10 - 20 seconds. When the engine sputters or "pops", you can see a orange color in the exhaust, but just for a second.

On the high end, the engine spools up fine with no sputter or problem. When it returns to idle, it seems to be fine for a minute or so, then the "popping" starts again.

Temp and engine RPM seem to be normal.
No air bubbles in the fuel line.

Any thoughts? As I said, the engine is new.

Jeff