Thanks Kestas,
I infer that the code set was an O2 sensor since the MB "service advisor" said it could not get a good reading that is why my Check Enige light came on. I guess the engine shaking like hell does not set a code (Ha ha. I have to laugh otherwise I would be furious with this guy whose first word to me after having the car for 6 hours were, "I have bad news". This is code for: We're going to rip you off). I have spoken to a myriad of people and most think it is entirely possible a collapsed cat could cause the engine to run poorly and prevent the car from going above 25mph. The guy who says it may be something else also said he usually can beat the dealers repair charges by 50%. OK his price is then $1250. hat is still high in my book. As far as further testing I got under the car today a wacked the exhaust with a rubber mallet and I did here some rattling. So my I am convinced it is a "pre-cat", but what do I do now? Thanks again.-Lou