[MASTERBrian]

I wondered if it should be in the other forum since the 99 suburban is mechanically the same as a 98 truck. If an admin wants to move that would be fine!

As for the cap, maybe I'll buy a new plug and test the wire. The cap/rotor are possibly lifetime warranty items I'll check.

I realize the external leak coolant leak wouldn't be a cause for this but everyone asks if coolant leak pointing to intake....Yes I have one, BUT don't think it's going into intake. That was my point.

As for sticky valve guide, would seafoam in crank case help with that? 270k mile truck....I don't notice any smoke, but she uses about a quart or two of oil between changes twice a year. She does have a small oil leak.

Maybe also worth pointing out, this is a true dual exhaust truck with dual catco catalytic converter going into dual flowmaster style mufflers and dual out the rear. I can not recall if the cats cross, but they may. The tail pipe behind driver side muffler rusted off, but rest of exhaust is good....Any chance that is enough imbalance in exhaust to create an issue?