Update......

I replaced the spark plug and the truck is running great. UNTIL....I got on the highway and my "check engine light" came on again. This is after I reset the computer yesterday.

So up til now, it was running great, and still is. So, I stopped by AutoZone again for a reading, and again I got code P0136.

I am guessing it maybe a fuel pressure issue now? Although the truck responds well?

I also checked the MAF, and the small sensors look clean to me? Or, can that be deceiving?