The cat converter started making a grinding noise from where the insulating wrap had degraded so I started movign on a replacement. According to receipts, this was a Catco unit I'd bought a couple of years ago (I thought I'd bought a Magnaflow but whatever), and is sold as a high-flow unit with larger cells. Searching around there are a few complaints about Catco and rattling so I figured I would try an OEM-like direct-fit unit from Maremont. The thing seems well constructed, it has the right shape and doesn't need any adapters welded on, and the shop says installation was pretty simple. All good.
Unfortunately I've lost all power above a certain level. For example if I'm doing 60 in OD down the boulevard it doesn't matter how much gas I give there is no responsiveness, no change in speed or any noticeable change in power output. With the Catco unit the car would accelerate and I could pass the slowpoke easily, now I am the slowpoke. It still has power from a standstill, but everything above that is pretty much wet noodle. Sucks!
I can see inside it, the honeycomb is clear. Maybe some of the padding broke loose but one would think that some of it would be flopping in the cat. Anyways the muffler is a Borla which is just an open chamber according to them, so anything that went in would probably blow right on through.
Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
Re: lost my top-end
Just disconnect the pipe behind the cat and go drive it on some deserted road. If power is normal, the mufflers plugged. If still the same replace the fuel filter. A plugged muffler will also have cool exhaust coming out, whereas a normal muffler will burn your hand if held close to the tailpipe. My bet is on the fuel filter, classic symptom. At 60 MPH and the pedal floored, it should down shift to 3rd gear. Is it doing that? If not, then the trans cable ( TV CABLE ) is either broken or misadjusted.
I gave the Maremont a couple of months, and while it did get smoother it never got good. The top-end never came back. Even low-end acceleration was stepped like brr-Brr-BRR instead of a smooth and steady crescendo. Gas mileage sucked too.
So I bought a Magnaflow, and had it installed today. Car is back like it was, smooth steady acceleration, and power everywhere in the band. Car drives like a V8 should