Searched - Converters plugged up?

My '06 LGT has 176,000 miles and has started running really poorly, major loss of power above 3500 RPM and won't rev past 4200 without popping and banging, revs increasing very slowly above 4000. (I don't run it past 4000 until I get it fixed). Problem is worse in 4th & 5th gear.

It has normal midrange pull once boost builds, so I'm thinking one or more of the cat converters is plugged. Which one chronically plugs on this car? Can it be readily "modified"? Help!

You should buy a down pipe from one of the vendors here.

It will be cheaper then replacing your catted DP.

Then get the car street tuned by a local Tuner. You'll get better mpg and more power.

Most of us do this any way's. You can get a Cobb AP and go to stage 2 map with the DP or get the cable for your lap top and go open source tune.

My tuner is a Vendor on here, http://www.tuningalliance.com email him from his site or PM him from his thread in the Vendor Forum here.

You should also check the turbo for shaft play.

What have you done for routine maintenance on the car, are you sure it's the cat ? This is not a normal issue with GT's.

Don't assume it's the cat. You haven't done any other diagnostics steps yet. Get your hands on a tactrix or vagcom cable and check LearningView and enable the DTC code reader also. Post the screenshot up here. The LV will tell us a LOT.

And stop driving the car hard for now... stop driving completely if at all possible until you figure this out. You could be hurting the car badly at this point.