I searched around and found all but what 2 of my RPO's mean D6F and E7Z. Does any one know?

 

Have you tried searching the forum for those two codes? I'm guessing probably not, because there are a couple pages of results just on this subforum.

All they really refer to are the speedometer/vehicle speed sensor hardware. Remember that RPO codes are specifically for ordering replacement parts. The only time codes like these become important is when you're ordering parts from the dealership. The guy behind the counter will have 3 or 4 codes for one part number, and 3 or 4 for another. They're nothing really important unless you need to replace speedometer gears, etc.

 

Actually I did search. I had about 11 codes that I didnt know when I started. I may have missed them I'll admit. But at least I attempted to search. Ok if they are spedo related can they help me remedy the fact that my spedo is 7-10 miles an hr faster than I am actually going?

 

Probably not... You could pull the tailshaft off your transmission and check the teeth on the drive/driven gears and see if any are missing or mangled, but I'd put my money on non-stock size tires. You'll get 5mph +/- just over the life of a tire. Having a slightly off size or sometimes even different brands of tires you'll have slight variances in outside diameter. Check the tag in the door jamb and see what size tires/wheels your car is supposed to have.

 

Acorrding to my rpo, I am supposed to have 245/50 16s and thats what I have. Im thinking about switching to 255/50 16s. That would make it worse no?

 

A taller tire should result in the speedometer reading slower then your actual speed. Since your current tire package has the speedometer reading high already, it might bring you closer to accuracy, but who knows if it'll really work that way. Maybe.