Exhaust Bellows

[Nhollis]

I'm New here.Thanks for letting me join. I've been reading a lot on posts here.And have already found a lot of good information. I was an owner operator for many years. I've only had 1 ISX engine in a 03 W900L. I've recently purchased a 09 Pete 389 with a 485 Cm871 non deleted Cummins in it. My question is about the exhaust bellows. My truck currently has flex pipe in place of the bellows. Will this interfere with the regin process.If so do I need to go back with the original bellows. Thanks Nick