Grey smoke at high rpms

[RETed]

I currently have an NA S5 with a supposedly rebuilt streetported engine.
I have racing beat exhaust and thats it for mods.

I'll let my car heat up, make sure the pressure is up and then drive it nicely until its at proper temp.
When I open the throttle, then get to about 5k or so, let off the gas, it will usually back fire and a trail of grey smoke will come out. Some times its greyish blue.
This will happen everytime I give 'er hell. But after I stop, go eat or something, come back and start it up, it might not do it.

The exhaust smells really rich, but when it backfires, its not an oil or gas smell, its much more strong.

I'm guessing its oil seals or it needs a full tune up. It has tons of power still and doesnt feel awkward redlining it either.
I was going to do a compression test, but that won't tell me if the oil seals are good or bad, correct?

[Hughes]

I currently have an NA S5 with a supposedly rebuilt streetported engine.
I have racing beat exhaust and thats it for mods.

I'll let my car heat up, make sure the pressure is up and then drive it nicely until its at proper temp.
When I open the throttle, then get to about 5k or so, let off the gas, it will usually back fire and a trail of grey smoke will come out. Some times its greyish blue.
This will happen everytime I give 'er hell. But after I stop, go eat or something, come back and start it up, it might not do it.

The exhaust smells really rich, but when it backfires, its not an oil or gas smell, its much more strong.

I'm guessing its oil seals or it needs a full tune up. It has tons of power still and doesnt feel awkward redlining it either.
I was going to do a compression test, but that won't tell me if the oil seals are good or bad, correct?