Slow acceleration sometimes on 1997 Chevrolet S10

Lately I have noticed my truck bogging down especially when it has sat all night or all day while I am at work. Although, it does this only sometimes which is the puzzling part. It just won't go when it acts up, then I can either shift into 2nd or just give it a minute, and it picks up. However, the other day it did this through 3rd gear. My Service Engine light came on the other day so I took it to the shop where he pulled a MAF Sensor malfunction along with lean on banks 1 and 2. What do you think?
I have replaced the 02 sensors, distributor cap and rotor, plugs, wires, fuel filter all at 100k. I only run royal purple oil, along with k&n oil and air filters. Replaced the fuel pump @ 30K miles. I just want my truck to run right, I'm not ready to give her up yet, although my wife would like to see it go.

1 answer
Not being able to drive the truck first hand it is difficult to guess without having performed diagnostic tests. I don't work on Chevys and the only reason I am responding is a friend of mine had a very similar problem,same conditions, he had previously blown a head gasket and the valve springs had failed. It was bizarre but the garage that checked it out said they had seen it before on the S10. Totally a guess. Have the truck properly checked out using a scan tool look at live information as the truck is drive, mount a fuel pressure gauge to the windscreen and drive the truck to pin point the problem.