I have a frst which will does not drive smoothly on part throttle.
if you drive below 50/60 mph it will stay off boost and perfectly smooth, up to 90 it will not drive smoothly. I went to stamford hall yesterday and cruising in the convey it was constantly showing boost of 3-4 psi and juddering. when it went above 90 it was fine. Managed only 150 to a full tank of petrol
spec is 2.0l zvh, kent cam, t3, stage 1 chip, 10 psi boost. any ideas welcome