2002 VW Bora 1.9 TDI
 

I have just bought a bora 1.9tdi 130 remaped to 170. I have noticed that when the turbo kicks in, In 4th gear the rev counter races like the clutch is slipping then it drops back like it has engaged. the clutch doesnt slip on hills or any other time. i was told it might be to do with the turbo. Any help would be greatly apreciated