I wanted to know if anyone has any suggestions on this. I've heard many different answers on this. Some say don't do it or check engine light comes on. Others say that as long as you leave tha cat on you are ok. I went to the Diesel Extavaganza this weekend and the tech with Shied Diesel told me that I would have to use the cat or engine would run poorly. Any suggestions would be appreciated.

I'd suggest reading through the exahust section (where I moved this to) and read all the posts about down/front pipes and with/without Cat.