when cruising in OD, i will push about halfway on the gas and the car will sputter and stumble to the point where it jerks back and forthpretty hard.. its only from1500-2100 rpms(+ or -)but ive also noticed it does it slightly at higher rpms but the valves dontmake any noise likethey doat lower rpms... could it be predetonation from running 87 octane and if it is, is it irreversable or will running the recommended 91 or higher fix it? thanks

 

I'd suggest using 91, probably isn't contributing too much to the problem, but you're loosing power because of it. I say this again, check your EGR and make sure it's clean and functioning correctly.

 

I don't think the noise you are hearing is valve clatter. Most likely the noise is pinging, probably due to using the wrong fuel and the EGR not working properly. The car was designed for premium fuel, read the owners manual. The pinging causes the PCM to retard the spark, which can cause stumbling & poor performance. Put some proper fuel in the tank, what ever you save in cost per each gallon is being more than offset by the extra fuel being used by a detuned engine.