We did that also when it first started doing the sputtering thing. It was slightly low so we added a little bit. Hi and Low pressures are where they're supposed to be. It didn't make a difference with the sputtering at all.

 

Finally got it fixed!!! I can say I am truly amazed that it was the spark plugs! I had put in a set of Autolite Platinum's about 5,000 miles ago when I bought it- before I was on here and read to use AC Delco exclusively. The engine runs even smoother now than it did before- with the A/C on or off. I was listening to it the other day and I thought I could barely hear a slight miss with the AC off in gear while standing behind it. Couldn't feel it at all from inside the truck and it drove down the road/accelerated perfect. Apparantly the very slight miss it had was just being made that much worse @ idle in gear with the AC on.