B4 gearing help?

[Speeed Freak:)]

Have a new, well 2nd hand B4, I've put a 9T in her but doesn't seem to fast on a 21 pinion so changed it to a 23 and better but still not great, had a look at the spur and it's an 87! Interestingly the car popped the front wheels up with the 23 pinion and not the 21? I would of thought it would of been the other way round?

Would totally changing the gearing around have a better result? I.e quicker?

Or do I chuck a 6.5 or 5.5 in?