Back end feels strange
 

I have just had Prodrive springs fitted to my 04 STi. On standard wheels everything felt good,. The ride seemed firmer but smoother. Last Friday I took it to Micheldever tyres and had the geometry set to Prodrive settings & a set of PFF7's put on with F1's 225/40/18. At slow speeds, round town it feels nice, but as soon as I start to push on (50-60) the back end seems to wollow. It just doesn'y feel right. Could it be the geometry or is it the tyres. The pressures were 33 front & 31 rear. I upped them today to 34/32 but have not had chance to give it a run.
If anybody has any ideas, please help.

easiest answer is to put your old wheels back on and see if its better/worse??

maybe they haven't set the geometry properly?? or could simply be the tyres 'bedding-in"??

alyn