'99 running rough / smoking
 

I went to start up my '99 Ram (24V, auto, 202k) this morning & I noticed it didn't sound right...almost like it was quieter? I hit the gas pedal a little & it started to miss & run rough. 2 seconds later I saw a cloud of white smoke come out of the tailpipe.
It seems to idle just fine.
The truck is stock except for a power puck & air filter / intake.
I can't see anything physically wrong underneath, nothing leaking, etc.
Any ideas on where to start?

OK I went out & unplugged the power puck & plugged the stock harness back in & everything cleared up & the truck ran fine. I took it for a drive & all is good.

I got back home & plugged the power puck back in, took it for a drive & still good...

I still don't know what could be wrong with it..