not long bought a octivia1.9td 2002 reg seems at times when get to around 50 hit a flat spot anyone have any idea why this happens cheers

Are there any fault codes?, sticking vane mechanism on the turbo, air mass meter on its way out.

Maybe. Which tune?

whats a fault code how do i go about finding out

You need to get it hokked up to a diagnostic machine or someone with vag com which is a PC based diagnostic programme