Recently Purchased and istalled a Magnaflow Hi Flow Cat Converter to the 2008 Impala SS, already installed on the car is a K&N Cold Air, Mass Air Flow Sensor, and Magnaflow Performance cat back exhaust.

I had the Local mechanic put the Converter in and since its been installed the car was a little sluggish and the check engine light came on, took it back to the mechanic they cleared the code and seemed to be running right again for about a full working day, Came out to the car late that evening and the Check Engine light is on again.

Took it back to the mechanic had them check codes threw the code -P0420 Converter Below Threshold Bank 1... Any ideas on how to figure this **** out, the mechanic seems to think its a faulty Converter (of course they do).

Anyone have any of these issues before also any idea on what to do? and sorry in advance if this has already been adressed in a previous thread...

 

Fixed.

Hope this helps.

Seriously though, you may need a bit of a tune to correct your fuel curve for the change in your exhaust flow

 

When you say a bit of tune what are you talkin about... should i buy a tuner; like hypertech or diablo or find a shop that can tune it specifically maybe a dyno or somethin to that effect.

 

Well a shop will have specific software like the hypertech, diablo, or SCT. I'm not 100% sure what is the "best" for the F-body guys, but my tuner is mainly a LSx guy and he tunes my Mustang as well using HPTuners and I have had absolutely zero issues with my tune, so I would reccommend that. You may want to get the opinion of some of the other guys on the site before making your final decision though. I'm just trying to help out to the best of my knowledge.

Edit: Just read your entire first post and realized that the code you were throwing may come with a P0430 after awhile because thats the same thing that happened to me after I did my hi flo cats. you may just need to have those codes turned off (if your AFR is right). Make sure that you leave the O2 sensors on though so you can still pass emissions if you live in an emissions area.

 

If the emissions test is an OBD scan only, you can delete the rear O2s with custom tuning and still pass.

Sometimes high flow cats will trip these codes. As suggested above, you can just delete them with custom tuning if that is your only problem with the setup.

 

Agree with RPM about deleting rear o2's but hi flo cats will not make enough difference to change your "fuel curve".