Fellow GM Guys: I have been having trouble with my 1996 Buick Park Ave when going up a slight upgrade on the highway and stumbling while at a light load @ 1500 - 1700 RPM. I'm looking for any additional ideas in what to check.
Here'* the history of what'* been done - Found that two of the coil banks where missing, so I replaced the Ignition Module and all three coils, Plugs (NGK Iridiums) are only 15 months old, wires replaced about 5 months ago, fuel pump and fuel filter replaced about 7 months ago, cleaned the MAF, checked and cleaned the EGR, replaced the PVC about 2 months ago.
Latest: I found that one of the plugs was missing when revving the engine to 1500-1700 RPM - replaced the plug, but now others are missing. I've replaced all of the plugs with Bosch 9601 Iridiums, and found that the NGK'* gap has increased from 0.060" to 0.062". I understand the Bosch plugs are a hotter plug then the NGKs.. I gapped the Bosch plugs to 0.060" - required gapping out of the box... So far, so good. I'll keep you informed.
Any ideas?
Thanks.

Don't use Bosch plugs. Even they admit their plugs don't work well in 3800'*. Go back to the cheap A/C delco 606'*.

good if its the sc engine but my non sc ones never run good on resistor plugs and they wear out fast. platinum or better. ive been running e3'* for probably 10-15k, first in my 3800 bonnie but probably the 4rth set ive bought theve lasted longer than ive had the car every time

Agreed, I have only used these AC Delco'*, but I hear NGK, and E3'* are good, I am pretty sure the AC Delco Iridium were in the car when it was manufactured.

i believe original was delco platinum at least in my car. you can get the e3'* for 4.80 at advance auto with the p20 in the cart and pick up in store.

How are those E3'* anyway?

03 monte 3400 i put them in place of the delco plat. and msd wires at 100k ran as good as it did new and gained 1 to 2 mpg, ran that way till i sold it at 170k

03 imp 3400 (my moms but i do the maint) exact same result but she still has it

98 bonnie non-sc put them in last year had 2 sets of autolite plat. in it between 100k and 160, never really ran like new when it had the delcos so i put the e3'* in it and it smoothed out and went back to normal mileage maybe slightly better. with a lead foot and a K&N drop in the wife gets 28 in rural two lane only commute.

i put them in a bunch of small lawn equipment and the change in starting and smoothness is dramatic especially in my stihl chainsaw

Duly noted Justin. Thanks for the info. Maybe I'll upgrade.