G
GTP-1
Guest
I need some experianced opinions. I can't beleive what I am seeing on my 99 GTP. I changed plugs the other week, took out the factory NGK's. I put in a set of Bosh +4's that are one range colder. I have the 3.4" pulley and CAI as the only mods. I noticed a huge drop in fuel economy right around the same time. The car has about 45,000 miles on it. I picked up some lost power with the plugs, especially up top. But what gives with the mileage?? Ideas?? I just got back last night from a 160 mile all interstate trip with criuse set whole time at 74mph. I clicked off a very pathetic 20.5 mpg. Can plugs really cause this much of a loss?? Car runs great and has lots of power and idles very smooth.