Originally Posted by Gumby22

Given the lack of power and sulfur smell you describe, as well as the vacuum test results, the cats are the most likely culprits. If you want a little more certainty, one other test would be to remove the upstream (closest to engine) oxygen sensors and go for a drive. Obviously you’ll have some extra noise, but if the cats are breaking down, you’d be giving the exhaust some relief from the back pressure, and power should improve.

As far as brands, Walker is the only one I’ve had any experience with. At work we don’t do extensive exhaust repair and refer customers to an exhaust shop we work with. Any time they replace converters they install Walker and swear by them.

We will also occasionally buy exhaust clamps and other necessary hardware/adapters/extensions as needed. Most of the stock kept by our primary supplier is also Walker and my opinion is they make good products.

Considering that converters don’t break down unless there’s excessive exposure to unburned fuel, oil or coolant, it really shouldn’t matter what brand you choose because they’re all built to the same specifications depending on your vehicle. That’s not to say there’s no questionably manufactured converters out there, but generally I wouldn’t stress about it too much - go with the name you trust.

That said, I don’t have any direct experience with magnaflow, flowmaster, or any other big aftermarket names. The work I do is pretty straightforward - part comes off, same (replacement) part goes back on, though not always in the right order. The mod and performance seekers in this area typically enjoy doing that work themselves.

One last thing to note - While I can appreciate needing to keep a budget, I’d really recommend professional installation unless you’re a very skilled welder. Besides most emissions states requiring converters to be welded in, the best way to keep the cats working efficiently (and to keep the CEL off) is to make sure they’re completely sealed. Welding is the best chance of accomplishing that.

Originally Posted by 09silverado6468

Hey y'all, I posted in another thread not long ago about loss of power. 2009 Silverado 4.8l Z71, 199,000 miles now. I narrowed the culprit down to the catalytic converters (so I thought). I replaced them and I did notice a difference but not back to the power it should have especially trying to pass at highway speeds. I just made a trip to South Carolina due to unfortunate circumstances and on the way back I noticed the oil pressure was reading about 25 psi at highway speeds and below 20 psi at idle. It would increase to about 35 when "getting on it" to pass. Shortly after the "change oil" light came on. I've changed the oil and the pressure is working properly now. My question is, is it normal to do that about the time the oil needs changed or is it about time for some engine work? I've never noticed it before. And could that be contributing to the loss of power?

Originally Posted by oilcanhenry

Probably have fuel diluting your motor oil. Rings are gone and fuel is leaking past them into the oil.

Originally Posted by 09silverado6468

ahh. Thank you. I kinda figured some repair was coming. The oil did seem darker than normal. Doesn't the rings usually cause smoke when going out or not always?