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Discussion Starter #1 (Edited)
A few months ago I gutted the cats on my 06 gto ( thought I might of had a partially clogged cat turned out I didn't) anyways this was early spring so the weather was fairly cool and I only had some backfiring when downshifting. NOw that the hot summer weather is here the car is backfiring when accelerating during shifts and backfiring a lot more when downshifting. I havn't had the car tuned yet because I am going to be doing some mods first. Is it Just because the car is running to rich without the cats? Would a tune help or are there other things I should check?
Thanks Justin
 

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I have no idea why people gut cats. You could have sold them for some pretty good cash. If it's back firing while you're accelerating I wouldn't accelerate hard anymore until you find the cause. One could be improper fueling and that could cause serious problems. If it's just when you let off and downshifting it's probably the DFCO kicking in which can cause back firing. It's especially noticeable without cats. It can be minimized but not eliminated with tuning then.
 

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Discussion Starter #3
Yes I know how much you can get for cats. That's why I boxed up the internals and took them to the scap yard. So If I am having a fuel system issue what are some things I should look for or test I can do? I will do a fuel pressure test before I drive the car next. Any other advice is greatly appreciated.
 

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A wideband O2 is your friend. You can also look at fuel trims altho they aren't as helpful. A gutted cat BTW is more restrictive than a straight piece of pipe.
 

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Discussion Starter #5
Yes a pipe will be going in place of he gutted cats. The only reason I did it was because I thought I was having a problem with them. The funny part is that the next week I took my expedition to the dealer because it had no power and turned out the cats were clogged lol. Any suggestions on the brand of wideband? And once again thanks for your help
 
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