LX450 give a small white smoke only on Gasoline not on LPG (LPG expert needed)

[at1992]

Hi,

I posted a few days ago that I have a white smoke coming from the exhaust pipe. Small tiny white smoke.
My LX450 is a 1FZ-FE engine. I do have LPG conversion also. So I was curious yesterday I switch back to LPG and no more white smoke. So this mean that the pipe white smoke only when I'm on Gasoline.

What this can be? Bad Fuel Filter? Clogged filter? I just replace the Fuel Pump today! Still smoke on gasoline a bit. What this can be?

Thank you