Guys, I have asked around locally with no luck, any help that can be provided is very appreciated. OK first off the car I have is a 95 TA M6 with the mods in the sig and lately it has been acting very funny. It dosent appear to be as fast as it was when I first got it, it was bone stock besides an offroad y pipe on stock manifolds. It has white smoke coming out of the exhaust when I go WOT, sometimes...not always. I got on it in front of a freind and he said it was white and then when I shifted into second it turned black then stoped. Motor has 98,000 miles on it. It also seems to be lacking in power under 2,000 rpms sometimes. I know it shouldnt have alot under 2 grand but sometimes in almost has alot less than normal and wants to act funny and stuff when I am cruzing along on the high way. It also seems to have alot more engine vibration than it has ever had before. It is also averaging about 16 MPG on an average of highway and city driving with 3.42s and getting on it rarely. Yesterday when I drove it in the rain at one point it would barely drive...you would give it gas and it would respond a second or so later and had no punch. Oh it also has a recent Opti change by last owner. Thanks, Brad
P.S. Sorry for makeing post so long.

 

The white smoke sounds like an antifreeze problem, like a blown head gasket. The black smoke could be oil, fuel etc....... If you have a blown head gasket it would make your car run a little rougher, as you are now getting antifreeze into your oil. Check around your heads and see if you can see any blown gasket or markers to show you of a blown gasket.

 

This might be a simple question but when did you last change the sparkplugs? If that are still the factory plugs your lucky they made it this long! Even if they are about 30K old pull them and see what they look like it sounds like your running richer then you probably should be, but Ian is normally pretty good and not letting that happen. So I think the dark smoke is due to it running rich on it's own, like fouled plugs and that sort of thing.

Normally if you blew the head gasket you would know about that in one way or another, milky oil, mucky coolant, overheating, and an engine that will seaze if too much coolant gets to the bearings... Ask me how I know!
I have had 5 blown headgaskets in a couple of different vehicles, not all of those symtoms show up at once, but they all indicate a blown head gasket.

So you thought you wrote a lot, I have 2+ paragraphes telling you to check your oil, coolant, and sparkplugs!

*** EDIT ***
I forgot to mention that the white smoke is more then likely oil and you may want to do a comression check if everything else pans out, but you can probably tell that by the oil fouled plugs as well! Good luck with it!

 

Black smoke-unburned gas (normal for WOT)
Blue smoke-oil
White smoke-coolent

 

It has plugs that are about a month old. What about the 02 sensors?