[oz 930 turbo]

Howdy all. Had my 2004 996TT in for a check up as never seemed to get the turbos to get past about .6 bar, mechanic said turbos are in need of replacement at some stage which is surprising as car only has 65000 miles.
I thought this is the perfect time to explore adding different a couple of mods to enjoy the car even more. What are the most common upgrade packages around without spending stupid amounts of money?
My understanding is that by changing the turbos to something a bit more modern, changing the exhaust set up and having a ECU remap that these cars can easily handle 500-550HP. Has anybody had any rescent experience or recommendations?
Cheers all