My friend just bought a 2000 prelude base, and just sometimes the idle on the car jumps up and down. The car does it after it is warm and has only done it twice so far. I checked the vaccum on the Idle control valve and it seemed fine. If it was the TPS would it not do it all the time? It is also getting some puffs of smoke in between shifts when he is reving it high. I can't remember for sure, but I think the smoke was white which would indicate over fueling. He had codes ran and it was showing a pressure drop in the catalitic converter, if it was clogged wouldn't it idle erratically all the time? Car has a DC header and a apexi exhaust and a no name intake. I noticed that the hose that was hooked up from the valve cover to the intake was by passing the the two fittings where the original lines hooked into, would this cause any proplems or are the other lines just some kind of drain tube? I did a search on this topic, but didn't get enough info.