My GMC suddenly started cutting out under load. I've noticed it occasionally missing in 3rd gear and OD so far and tried to get it to do it in 2nd yesterday afternoon but never could. Doesn't idle rough (had it tuned up about 5k miles ago at the dealer) and it's doing this around 2300 RPMs, generally on a slight uphill grade.
It ran so smooth in 2nd yesterday that I'm wondering what 'emissions' type devices might be causing something like this. (noted the missing BTW as something that almost feels like a sharp wind hitting the vehicle with a momentary dip in the tack reading). Any ideas folks?