Advisable to fit uprated rods as the ones them are no stronger than the normal 8v/16v engines, you can get some for about £300 (Eagle, iirc) have seen them bend when around 300lb/ft torque.

Other thing that happens is the valve heads fall off, Supertech one piece valves and retainers sorts this.

Can suffer from boost/vac leaks as the rubber pipework under the inlet manifold can leak.

If still fitted with DMF can use solid flywheel from G60/mk3 16v etc and a VR6 clutch.

In the early days of the 1.8T Jabbasport had a couple of demo cars with their IHI Turbo conversions, which used a VF34? turbo with their own manifold and around 330hp, drove one of these conversions in an Ibiza and it was rapid. Think they were on standard internals back then!

One guy I know Bill Brockbank had that conversion in his Ibiza and went to the Pistonheads vMax thing at Bruntingthorpe where they have 2 cars race down the runway and timing beams. His car did about 159mph from memory and beat quite a few supercars that were there on the day. He has since built the car into a race car for Castle Combe saloon car champs and it ran a GT35 on it and around 500hp, crashed it at Combe though. He now runs a tuning company and is quite knowledgable with the 1.8T, based nr Gloucester.

https://www.facebook.com/Badger5Ltd?fref=ts

Lots of tales of woe and advice on there.