I am getting the flowmasters 40s and deleting the resonator and replacing it with 2.5 pipe, do you guys think this cat will work good with these mufflers, or will it take away the sound of the flowmasters, I do like the magnaflow mufflers, just my opion, or would you go with a different cat, let me know your thoughts. Will this sounds pretty good, let me know.

All I know from experience is that what your going to get is one loud Bonneville with a LOT of interior drone.

Other than that it will def turn heads.

What year make and model Bonneville do you have?

What year is your car? Removing the resonator can cause the exhaust to become raspy. A free flow cat will deepen the tone a bit.

just put a straight pipe in lol

Depending on the year of your car, some after market cats can throw codes. I went with a Goerlich because it was recommended at the muffler shop as guaranteed not to throw a code on my 2000 SSEi.

I had a 96 SSEi with a High Flow 'Magnaflow' Cat 3" that threw codes all the time.......

3" Magnaflow here, and no codes ever.

its a 03 ssei,

For a 03 you will need the cat purplehazier mentioned.