I have a '94 S4 with a stock exhaust system. I have been thinking about tweaking it a bit, but not to the extent of ripping it out and installing e.g. a Stromung system.

A few questions:

- How much restriction do the stock catalytic converters impose when new?

- How much additional backpressure do 10 year old converters cause?

- Who makes a good aftermarket high-flow cat?

- What kind of backpressure reduction is possible while retaining converters?

- To measure backpressure, is it really as simple as plumbing a boost gauge to the test port after the turbo hot side? I can sort of believe that the air column in the tubing will isolate the gauge mechanism from the exhaust gasses, but it still seems a little weird.

Thanks in advance. Even partial answers appreciated!