blue smoke generally means oil being burnt, white smoke is usually water.
red smoke means someone stucka flare up your exhaust
might just be the decats and everything settling in. when was the last time you checked the oil level? what is the oil level? is it less than when you last checked?
this first simple tests tell you if your car is using oil. if it is the next thing to work out is where is the oil going.
oil can be used up just through engine wear, so don;t suddenly panic, might mean you need to run a thicker oil.
if it is using oil i would suggest a compression test. it will tell you if the cylinders are holding compression and if not which cylinders. this might be due to wear of the seals. this would mean oil is coming up from the sump and being burnt in the combustion process.