What are catalytic test pipes?

[xcracer450]

ok im looking for a new exhaust for my 2006 6.0 and i was lookin at mbrp's web site and they say that there systems "permit use of catalytic test pipes"....what does that mean im also loooking for turbo back system that deletes the catalytic converter and offers a muffler delete pipe and has a 3.5" downpipe so i dont have to modify the firewall....I know someone has the answer thanks alot

[tbsimmons]

Test pipes are delete pipes.

[dieseldan]

talk to roland at rbp in corona california they have great exhaust and muffler and cat delete pipes available and much better quality than mbr