so I would like to replace my cat on my truck cuz its stock and old and i think its rattling. What i wanna do is keep stock manifolds for now then where the cometogether to go in the cat I'd like to put a y pipe and then run that to magnaflow high flow cat, to a magnaflow performance muffler and maybe out the side? But what i wanna know is what size is the piping from the manifold where the 2 pipes enter the OEM cat? SO i know what y pipe to order

 

what engine?

 

5.0 sorry :p

 

they make them i think in 2 1/2 in pipe my I6 has a 2 1/2 in y pipe into one i don't see why not

 

so i could go like this:

stock manifolds
2.5'' y pipe to
2.5'' high flow cat to
2.5'' magnaflow performance muffler
and out the side prolly

u think that will be legal?

 

i know it would be legal in Maine i have 2 1/2 inch pipe all the way back.
ask your local police officer they will know

 

but you are 100% positive that its 2.5"pipe?

 

Same, i have 2.5 pipes form the cat back, just get the adapters if your clamping with some exhaust sealant compound or weld it to make it look nice and clean.