My bonneville has 140,000 miles on it and I have done extensice work to it in terms of maintenance and performance. My car is supposed to have 225 hp stock but as of now it has 235 or so give or take a few HP because I am using a g-meter. Anyway, I have added a cone air filter, NGK plugs, superchip, exhaust plus replaced the sc, cleaned out the TB, replaced fuel filter, o2 sensor, prob more but I cannot recall. My question is, with all I have done, why don't I have more HP? I am thinking that the timing belt might need to be changed. I don't know if it was ever done. I think it might boost my HP cuz my engine is losing HP from the timing belt. Also it might boost MPG. Let me know what you think. Thanks