[Biturbos4] smoke at high revs

[mike]

A bit of list wisdom needed please gents.....

Car is ’99 S4, 200k miles. Problem is lots of smoke at full throttle above about 4.5k, it’s sudden rather than gradual onset

Runs & pulls fine otherwise (but obviously staying below 4.5k), it might be paranoia but I think I’ve also got a slight roughness/unusual noise on the first start of the day but that clears after 20 secs 

Any & all thoughts welcome