My truck is a 1994 with a 4.3 Vortec HO engine. Mods include a high flow exhaust including the cat; Accel cap, rotor, wires, and coil; 3 piece under drive pully set; K&N FIPK intake kit; and the heads have been milled and rebuilt. The truck runs GREAT once it is warmed-up but prior to reaching operating temp. it runs extremly rich (black soot out the tail pipe). Any suggestions or ideas? Thanks for any help anyone can provide. One other item to add is that there is NO check engine light on so the computer thinks everything is OK. Thanks again for any help and ideas.

Bill

Bill,
what plugs?
heads milled= "new" engine.
compression chamber and "squeeze" has changed,
so you NEED the coldest plugs available.
also, might unplug fuel pump relay for 10-20 min. to allow
MAF to reset air/fuel mix.

hope this helps,
chris
nrt racing

Check your timing with the timing wire disconnected.

You might have a CPI injector going bad, search for cpi injector in the blazer forum for more information.