Limits at 4k??? You mean when you floor it, itll bounce of the limiter at 4000 rpm in any gear? Thats well dodgy seen as the RT dont have a variable limiter to protect the engine, it should kick in at 6500-6750rpm. Sure its not a diesel youve got under the bonnet, lol
Id go ask Reno whats up, see if they know, then take it to a decent garage to get it fixed.