Oh I forgot to say so, but I did change my oxygen sensor also. I did it all at the same time when I changed the cap and rotor, wires and plugs. So I can't tell you for sure how much it actually contributed to my horsepower gain. Also, this engine does not have a "crankshaft position sensor", but they do have a "throttle position sensor" on the carb. Not sure exactly what this will do though. I also pour a bottle of fuel system cleaner in my gas tank like every 6 to 8 months. It reduces carbon buildup in the engine. If there is any black smoke at all when you start your engine, then you have carbon in your engine. I couldn't even see it until I was standing behind my car and I used my remote start. It wasn't a lot, but it did puff out a bit a black smoke right at startup. Another thing that I wanna do is chop off my catalytic converter. (Yeah I know its illegal, but who cares) My brother used to have an 82 cutlass 4door with a 3.8 v6 and he cut the converter off and had just a muffler on it. The damn exhaust sounded like a v8! It had a bit of a throaty tone to it. It also had a good bit of horsepower. He was always screeching the tires with no problem. I wonder if the converter being gone had to do with it. But on the other hand, his engine had been rebuilt by the previous owner less than a year before he bought it.