That would definitely cause issues. Poly bushings don't flex like rubber ones do so if you swap out the rubber for poly you need to have a way to guarantee that there is no friction between the poly bushing and the cam-bolt that holds it to the car. This is why poly LCA bushings must be used with hollow greaseable LCA pins so the bushings can rotate freely on the pins as the LCA moves up and down. Also why you see grease fittings on aftermarket UCAs that come with poly bushings.
Looks like you found the problem though and are on the right track... that's the extent of my advice lol I don't have much experience drag racing, my '70 Duster is being built for road racing.
