after market silencers on over bore engine kits

i have been wanting to put a can on my summit ever since i installed the kit..but talking to the builder of the kit he suggested leaving the stock one on because the aftermarket ones didnot have enough flow .. however upon doing some research this morning ,the company that is building a can that he approves of has a online parts list that shows the same part # for all 800s, ho.s and r.s which is no big deal .. but it also shows the same # for the 600 ho . so i guess what i need know ..does the 600ho have the same back pressure requirements as a ported overbored 800.. ??? or am i being sold a line of bullsh..t ??

or maybe i should pull the can off my sons 600 renegade .. it has got a hot dog cooker on it to boot..lol