Sound like the car is over boosting and going in to limp mode where the ecu limits the boost the car produces and resets when turned of and on.
The car needs to be scanned or connected up to VAGCOM to see what codes its showing but to be honest I would have it looked at by a specialist company to find out what’s wrong and don’t buy it till the owner finds out.
Any work on the turbo means the engine will have to come out and that’s major money.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
04 Audi A4 B6 1.8TQ S-Line 190bhp 6 Speed Duel SMIC
Milltek Exhaust|VMR boost Gauge|SP51 K04-15 Outlaw (K04-23+)|Samco Sport DV|034 Sport CAT (15bhp over stock)|TT MAF| 380 inj| Autobahn88 TIP|
To be fitted: B7 RS4 F-Brakes|B5 RS4 R-Brakes|SB Stage4 Clutch|