""Meineke put on (they actually put on two cats) are too small and thus restricting the outflow from the turbo.""

Define too small? Diameter? So what your saying is, Meineke used 2 reducers on you car. One to go from the 2.25 downpipe to something smaller and than another to step it back up? Something does not sound right here. How much do you trust your indie shop? FYI 2 cats does not cause more restriction. This is basic fluid dynamics. I would look more at whats inside the cats and how long each is. A lot of import cars use 2 inline cats, or rather a pre-cat and a cat. How about a picture. I think that would be worth a thousand words. Oh, as for testing look at exhaust gas temp more than pressure.