sounds alot like tire balance to me... hitting a pot hole can sometimes knock off wheel weights. Did this start before or after you had the work done?? Have you tried swaping the rear tires to the front to see what happens??
NEVER do business with Sam Rivera AKA Sam Wilson of Rivera Race Chassis. Paid 2800 to put car together. NO work was done, never gave back my turbo kit. Now I see old adds of my parts being sold on craigslist while car was at his shop.