poor acceleration

I'll try and make this short. 99 s10 4.3. stopped running, changed out fuel pump, couldn't here it running with key on. then it still wouln't start. pulled #4 plug wire off to check for spark. cranked it over to check, started up. put plug wire back on, won't start. changed cap,rotor, plugs and wires. did all ingnition checks too, all ck'ed good. started right up. two days later ses light came on on the way to work. started it up to go home no ses. But runs like crap. put scanner on it, came up with code p0452. Ichecked all lines, hoses ect. checked pwr tp purge valve, good. Change out fuel cap the funny thing is it seems to run alright in the morning, then in the afternoon is when it starts acting up. any suggestions. ses light hasn't came on again. when it runs real bad, hook up scanner, sometimes 0 codes or the same p0452. i

The air is heavier when it's colder so your truck will naturally run better in the morning.

My guess is that your air filter is pretty dirty causing your problem