Cold start noise Golf Mk4 1.8T 150 GTi

Wondered if anyone could advise...I have a 00 X Golf 1.8T 150 Gti (97k) which on cold start up sounds like the exhaust has blown, it also struggles to tick over so I have to rev it. It is incredibly noisy whilst it is doing this!

This lasts for a few mins until the choke cuts off and then it returns to it's usual smooth quiet tickover.

I have had the exhaust checked and there is nothing wrong with that, it does appear that it is somehow connected to the choke as it only ever does this on cold starts. :1zhelp:

if you have the secondary air pump check for leaks at the pump and the pipes