Chevy & GMC Vans

I doused the MAF sensor with this stuff. I even used it on that little sensor right behind that (does anyone know what that is/does?). I was in such a hurry putting everything back together that I forgot to plug these two sensors back in and drove off. Interestingly, the engined behaved exactly the same. (The only difference I noticed is that it was slamming into 2nd gear. I didn't know this could affect transmission like that). Anyways, I plugged them back in and there's no change.

I left my van at a shop and asked them to look at the catalytic converter. They didn't think there's anything wrong with it.

So, the troubleshooting continues...

I took it to a tranny expert, and he doesn't think that's the problem.

Got DTCs:

P0102: Mass or Volume Air Flow "A" Circuit Low
P0101: Mass or Volume Air Flow "A" Circuit Range/Performance

I broke down and took the van to a shop. It had a CMP retard (cam timing) of -15 degrees. Apparently the timing isn't adjustable on my engine, so the guy said he drilled out/slotted something to get it back down to -2. The difference is very noticeable. It has much more power now AND it runs a lot quieter! $176 + tax. Money well spent I think.

That little sensor behind it is the intake air temp sensor.

Well the problem is still sort of there...

Could this be caused by weak ignition? How would I go about diagnosing for that? Does a weak spark generate any DTC's?

I've never checked the spark plugs, so that's something I could do.
What are the other components are involved. I've heard of something called a coil pack. Is that expensive?

Also, how would I know if the poppet valves are going out?