hi, all. recently my 87 190e 2.3 8v broke it's driveshaft and flex-coupling at highway speeds. Consequently, the rear housing of the transmission was cracked, the O2 sensor was demolished and the cat was destroyed too. My esteemed tech made the necessary repairs using his parts car for what he could, and a few brand new parts aswell... it cost me a mere 1000 bucks, a steal. Heres the problem, i soon noticed that the car was very sluggish all over the rpm range, and it was using way too much fuel. It also developed a howling exhaust sound from the cat. Took the car back told him the symptoms. He seemed most concerned with the fuel consumption. 250$ later, i had a brand new O2 sensor (the one he replaced the broken one with was used). The car now gets decent mileage, but the power is still lacking (i got dusted by an old couple in a dodge shadow today). When I asked the tech what the howling was, he said that the cat he used on my car was hollow and had "no filter in it" and it was off a 2.6 motor. i'm weary of this.... my car's got a little more bottom end with the new O2 sensor, but anything over 3500 rpm leaves it gasping. i'm fairly sure that the engine relies on exhaust backpressure to run properly, but i'd like any advice i can get.

thanks alot.

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100 km/h is unsafe... it's fast enough
to kill you, but slow enough to make
you feel safe.