whats up with my motor?!?!?

ive got a 92 b2200 with 160,000 miles, i smokes like a motha in the morning and after work (after sitting for a while) but while it drives it doesnt smoke a bit. well i thought it was the valve seals so i replaced them two days ago and it still smokes. what could be the problem? should i just get the head freshened up? any info is appreciated.

Chris