It should be very inexpensive to have the cats replaced with a straight pipe. You can get the pipe for 30 bucks or less. I can't imagine you guys don't have a welder in the shop and somebody that can weld decent. Should only take them 30-45 minutes to cut the cats out and weld in the new piping.
2008 135i - MHD/JB4, MS DP's, AMS IC, UI CAI, CDV delete, M3 control arms/Links, RE Toe Link, ECS Trailing Arm, M3 rear SF & Trans bushings, SS brake lines, Michelin PSS.