Greetings! I dont have any specs on a US41. Whats your alttitude. I swapped-out my ST .91 to a Saito .100, much better performance. Reinforce wheel pants with thick fiberglass to mount them strong. My Stinger is excellent and darn near immaculate in finish, again , i wish i knew how to post photos on this site , i would send you a photo of it, done in an american flag scheme, its really sharp!!. Beef up your firewall with cut "45s". reply please, MjS Oops! , remember, my stinger is a 60 size!