My 97' Z24 has 76k on it. There are some small but annoying problems that I've been having with it lately and I'm getting tired of living with them. Here they are..

• The car seems to decelerate very quickly when I'm on the highway and I take my foot off the throttle. It's as if there is some mechanical drag on the car, but I don't know what it can be.
• The car's low end torque just as good as it used to be.
• The car's idle is intermittently rough.

I've performed maintanence on it relatively lately that should preclude some of these problems, such as:

• I replaced the plugs and ignition housing (distributor) about a year ago; they can't both be shot already, causing the rough idle (or can they?..)
• I had the catalytic convertor changed around 6 months ago because the original was failing, causing a CEL and overly high emissions (I was failing my emission test). So, it shouldn't be an aging cat convertor that is causing an exhaust restriction, reducing acceleration and causing the engine to decelerate quickly from highway speeds.
• I Sea Foam'd the crankcase and fuel tank/injectors, so there should be less oil passage sludge inducing a mechanical drag on the engine, and the fuel injectors should've been cleaned to some degree.

So... my intuition would be that the maintanence I've performed should be precluding my problems- or should it? Something's still obviously wrong but again... I'm at a loss as to what that is. Tell me what you think.

Well Bryan: Its sounds like youre fuel pump could be the problem, How long has it been since you have changed youre fuel filter? What happens is people dont realize the fuel filter hasn't been changed in years. Another thing for sluggish performance is throttle body is dirty with carbon, You said you used Sea foam product, In which got rid of most of the carbon. I would get a fuel pressure test done on youre pump to see if thats giving any trouble. If there is nothing wrong with thw fuel pressure test on the pump keep us updated to keep discussing.

Good Luck

Thanks for the feedback.

I went to change the fuel filter, but when I removed it and compared its weight to that of the new one I just bought, it seemed to weigh the same, so I just put the old one back in. So, I was working under the assumption that if the fuel filter is light, it's not yet filled w/ sediment, and it's therefore still "good". If it should be replaced solely on the basis of mileage, let me know.

I cleaned my K&N conical air filter twice (it was really dirty) and now the car seems not as sluggish.

I'll clean the throttle body tonight or tomorrow, and then go from there.