ok lets take a deeper look then he also said that it could be a o2 sensor… hmm if thats not reading right the ecu is going to compensite for what it is reading.
soo first before you do a whole slew of things nyspeeds trainwreck says to do. i would pull the 02 sensor and give it a close inspection clean it off and you can put it back in or even go look at buying a new one if you are not low on cash or feel like replacing it just because its a 94 and a gm truck.
then you can look from there. have you replace the pcv valve at all? if not thats also a cheap fix alot cheaper then a o2 sensor but also deals with the vacuum line and the charcol canister.
your welcome that i added my .02 cents mike?