I'd say $50 bucks tops....since all they are doing is cutting out the gooseneck and welding in a piece of straight pipe. Plus...if you have great motor mounts...you don't even need a flex.
Define great. Like, solid or what?
2001 Regal GS, PLOG, 3" DP, 1.9's/L76 springs. 21* of timing on a 3.4"