wheel vibration problem

[SoNiC]

Ok, so i'm trying to help out my friend with this problem for the past few weeks, but still no 100% solution.

My friend just got some 19x8.5 and 19x10.5 wheels with 235/35/19 and 275/30/19 on his boxster. The wheel is hubcetric since it fits good on the hub. when we first install the wheel onto the car......the car has a very bad vibration from the steering wheel starting 45mph plus. our first solution was check the wheel balance on a better computer balancing machine. And the second thing we did was check the toe and camber of the car....since the stock size tire was 205/50/16 and 225/50/16.

after correcting the toe, camber and balance....80% of the vibration is gone....but still not perfect. I understand the wider tire will give it more road feel....but there are still some vibration from the steering wheel. Now the car seems like is driving on a rough surface all the time....and the vibration is mild but it gets worse as the speed increase. the vibration now starts from 85 plus....and once it hit 100mph...the whole car vibrate like a honda civic.

any idea? any suggust is welcome....thank you