Hi watkins, i've tried having a read on the TDI club about some tuning. It seems a mixed response about what turbos can be used. Some seem to think you could possibly use a VNT15 but the ECU will need some alterations to control it.

I wanted to change my GT15 to a VNT (power gains at the most would be 5-10hp as it can sustain a highier boost and also reduces turbo lag)

However it seems apparent that the GT15 turbo was used a lot on the 90hp TDI's such as the mk3 golf, and they all seem to upgrade their turbos and parts using a T4. So i'm going to start looking at what turbo upgrades they use on the mk3 golf tdi (but obviously its easier because they use a 4 branch manifold and not a 3).

Still interested in following up what you find out because i already have a custom code phase 2 remap, so if i wanted a new turbo and other mods i don't need a new remap, just pay a bit to upgrade to phase 3.
 
Haven't really looked into too much, as rather keep the costs down, using as many OEM parts of other vehicles as my car is my daily run around.

JBS have mentioned about NOS for that 'extra boost' but thats looking around the £750 mark with a progessive controller so my gearbox isn't killed.
 
as the 1.4 is a bit small I'd look for a VNT turbo to minimize lag,,, shadowmaker effectively converted his van from wastegated to vnt turbo so it can deffo be done,,,
 
A gt1749v will do the job.. lag less and 150bhp easy..

The only thing you need is a 3-1 manifold with the 3 bolt flange and a downpipe..

Btw the new 80hp DPF 1.4 TDI's have a vnt turbo..
 
are all of the later 1.4tdi 80ps vnt turbos? because myns the later engine but i dont think it the DPF one, as i though thoes were only on the "ecomotive"??