My '90 has never wanted to perform well until it is warmed up(temp to midway), regardless of the time of year it is. I let it warm up about 5 minutes or so to either cool off/warm up the cab and go.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed