one of the converters on my Expedition has started to rattle. Rather that replacing it with a stock setup or Magnaflow bolt in I have decided to go with two high flows. My original plan was to use the Magnaflow 94306s, as many on here have done. I talked to a local shop about it and he recommended 2 of the Magnaflow 99006HM, the specs look the same however the 006 is listed as heavy metallic. What is the better choice?

 

Go with the HM, they are more resilient to misfires. That's what I have sitting waiting to be installed, but for a Dodge Ram 5.7L. Ceramic substrates are damaged far more easily.

 

x2. Sounds like your exhaust people actually know their facts and recommend you to the right path. Glad to see its still out there.

The HM series are more durable like OEM. The hi-flow units recommended here over the past few years are junk and end up failing in twice the time it takes an OEM one to fail, but, they do add a good amount of volume to the exhaust.

 

How is the flow on the HM vs the 94306?

 

I checked with Magnaflow and indicated both converters have densities around 400.