[turbo mc kwek]

The smoke is light grey and smells like gasoline..

I'm not trying to be a wiseguy, but I'm pretty sure it's gas...

The engine doesn't have any oil in the coolant, coolant level stays the same, no sludge in the oil system. Even the oil filler cap is perfectly clean on the inside. There's no abnormal vacuum on the filler cap or dipstick....

Tomorrow I'll put the stock manifolds (with the catalytic converters) back on and take the car for a drive to see what happens...