Need Some Help

I found out from a friend that my car smokes black smoke from my exhaust when I take my car up to about 4k rpms or higher. I have a 98 prelude. I tried finding out about it last night buy reving it high but there was no black smoke coming out. So i'm guessing it doesn't happen every time only sometimes. I know its not my rings cuz i think if it was my rings the exhaust color would be a blueish color and you can't mistake the smell either. If anyone can help i'd appreciate it. I'm not really sure if its a big thing or not but I rather be certain about it.

Is it a continious pouring of smoke, or just like a puff when you floor it or down shift to a high RPM? I ask because when I first got my 94 prelude, I had this happening too...just a puff when i down shifted. I had many people tell me that this was carbon deposits on my cylinders or valves, not sure which, burning off, and was actually good for the car, just because those deposits were burning off. It didn't do it for long, so if your problem is anything like this, I wouldn't worry too much.

Its just a puff coming out when i shift high RPMs. Thanks for the input