2000 Suburban Misfire, Lean, Evap Leak

I have a 2000 Suburban LT1500. My wife was driving it and she said it lost power and left her on the side of the road. She called me. I told her to try starting it up. It did start, ran fine and she drove home.

I ran out and bought an Actron code reader (neat gizmo). I got the codes:
P0300 - Multiple/Random Misfires
P0442 - Evap Leak (small leak)
P0174 - Lean mixture (bank 2)

All I/M sensores were "ready" or "not applicable"

About 20 minutes later I went out and started it up again and re-read (I had not "Erased" previously) and only got the P0300 and P0442 codes.

Any ideas. I was reading threads here and it seems that the various codes can be explained by a whole pile of stuff. I was wondering if this combination of codes/info points to anything in particular. Oh, By the way, we just got the catalytic converter replaced and also they separated the trans from the engine to replace seals. Any clues?

Thanks,
fatpigdog (forum newbie)

For the evap leak,take it to shop that has a smoke machine.The smoke machine is the only way to find the evap leak and it does find it.Do not top off the gas tank,it wiill set the lean mixture code off.The evap system needs some space