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