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Debbie Harris's 1969 Grand Prix

2022 September
of the Month

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99 grand am gt exhaust modification help

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Im looking to upgrade the exhaust on my 99 grand am gt, im upgrading to a 2.5" exhaust setup from the stock 2.25" setup now, but im having difficulties finding a cat that would fit and has the same size piping for my car that i want to upgrade to. Should i get a cat with 2.25" pipes and weld it to the 2.5" setup im doing or os there a cat out there for my car that has 2.5" pipes? Any help and/or advice would be greatly appreciated

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Sounds like your building your own.  You can use your original (if its in good shape) and get an adaptor from any auto parts store. Less than 5 ducks.  Or many places sell universal CAT's in your size.

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Are you installing headers too or just the catback?  If it's just the catback, I say just get an adapter and keep the stock cat.  I have the SLP catback on my GAGT which is 2.5" and I've only ever had the stock cat on it and now a Cali carb replacement one.  I've had the SLP for about 8 years now with a stock sized cat and she still sounds wonderfully mean.  She sounds similar to a V8 and the GAGT actually purrs louder than my G8 GXP with Solo axlebacks for now. 

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SEE, Cat's N Ducks can get along.  Who knew? :lol2:

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