Just had jet coated Breathless Long Tube Headers, Bassini X-pipe, and removal of the precats done at Tony's Corvette Shop in Gaithersburg, Maryland. I retained the stock titanium cat backs since they are light and a defining part of the Z06. I understand they are well engineered, and not much is to be gained from a flow standpoint/hp standpoint from the catbacks other than sound and loudness. I chose the BPP headers since the are match ported to the oval Z06 exhaust port, increase hp/torque in all rpms on stock motor, and have removable collectors for easier clutch access. I had the car lowered maximally on the stock bolts with realignment to stock specs. The sound is much improved: hollow and more aggressive at idle, quiet at cruise (possibly even quieter and smoother than stock), and mean and loud at open throttle. It screams wide open, with absolutely no resonance at cruise in sixth gear at low rpm. There is no question in my mind that there is significant performance increases with these mods. SOTP feel is much more than doing the intake in my opinion. I believe the hp/torque claims on the Breathless website. That was done on a '02, so '01 may get even more since you get 5-10hp from removing the precats. I highly recommend these mods ('01 especially), and the emissions should be fine with the standard cats in place. I also guess there must be at least a 20 pound weight loss with these mods. Lowering the car with alignment is also highly recommended, since the Z06's come on the highest suspension settings from the factory. The cars sits much better now. Tony's shop did a first rate install with excellent service. I wish I did this sooner!