Tires For Boxster S

[aramati]

I purchased an 01 Boxster S. I need advice regarding tires. This is what's on it now:

Front: Dunlop SP Sport 9090 N-0 225/40 ZR 18
Rear: Dunlop SP Sport Super Sport Racer 265/35 ZR 18

I noticed the mismatch when I experienced a front wheel vibration at about 70 mph. A Porsche Dealer in Tucson (on my way back to Vegas) balanced the fronts. It moved the vibration point to 80 mph. The tires still have about 4K miles to go.

Here are my questions:
-Is the mismatch causing the vibration? Do I need a better wheel balancing job? Do I need new tires?
- If I need new tires what would you recommend for a combination performance for street/Auto-X?

Your advice will be much appreciated.
Regards,