As I'm reading your original thread, wheel balance is going though my mind. In another post, you said you put used slicks on your car. Granted there may still be a ton of meat remaining but they are used and had pickup on them when you had them mounted. With a more dialed in suspension I'm sure you are finding that it is now way more sensitive and is giving you more feedback than ever therefore the vibration is now probably more amplified. If this were my situation, I would start with having the tires road force balanced. Having the tires balanced with load will give you a true gauge as to whether or not your symptom is tire related or is suspension related. A lot of tire shops still do not use this method because to do it correctly is very time consuming and most tire shops are production based. So your best bet is to try the higher line dealerships, Mercedes Benz, BMW, Audi etc... That's where I would start.

Thanks for all the suggestions guys. I'm in rural PA, not sure where to find road force balancing.
There is Eurotire an hour away in NJ that I could try, I'd have to trailer the car there rather than drive on the street with slicks. One rear tire in particular had a ton of rubber slag when I balanced it and may be the guilty tire. Thinking back, there was no real vibration in the steering wheel so it must be the rear. I'll report back when I figure it out.

Don't trailer the car, just throw the wheels in the back of your truck or car. I would think that Knopf on Lehigh St in Allentown would be closer than going to Jersey. PM me if you ever go to SPR, I may be able to give you a hand.

I thought the suggestion was to balance the wheels on the car. Yes, Knopf is closer but I have an inherent mistrust of dealers, I use them as a last resort, rather use qualified independents. I haven't been to SP in about 2 years, I'd like to make it to one of the Potomac DEs in the Fall.

So I got around to dismounting the track wheels tonight. I may have found the source of my vibration: 1 rear wheel lost 2 wheel weights and another weight moved an inch. The other wheel also had a weight that moved. All the rubber slag is gone so I will re-balance the wheels tomorrow as a start I usually tape wheel weights but misplaced the alum tape.

Follow-up to my vibration issue after track event this w/e. The vibration was due to the lost wheel weights the last time. After re-balancing and taping the weights, the car was vibration-free all weekend so the spacers were not the issue.

Steve, that is great to hear. I am glad for you that it ended up being something so simple.