First off-Sweet 911!!! Love the color.
Some soft compound tires tend to aquire flat spots while sitting for a few days. My Sumitomos seem to have this affliction. I have a similar issue with a vibration that will go away.
How many miles on your tires?
The different color undercoating MAY indicate damage repair at some point.
The different front and rear brands of shocks isn't a big deal unless they are worn out. If the records are correct, one set or all 4 are at least 10 years old. Again, that doesn't mean to toss them out but just something to look into.
I have KYB in front and Bilstein rear shocks.
Are the Cup wheels factory, requiring offset adapters/spacers or aftermarket versions that fit without adapters?
Hope this helps as I know that a vibration can drive you freakin' nuts!!!!
EDIT: You should look into having your car lowered to Euro specs or close.
Also, I think 40 psi in the rear is too high. I would rather see around 35 or 36 cold. The front should be fine at 29. Someone posted that you should only have ~5psi front to rear for optimum handling. Track use usually requires much different psi based on tire compound, track temp and other factors, including driving style. Yours is, I would believe, mostly street driven.
Sorry, I didn't mean to write a book as a reply, the thoughts just seemed to start flooding my brain as I typed.