Will the stock Cat fit on a 3" downpipe&exhaust system

[Anomoly#5]

Im Just getting started on modding my DSM, I have done the free mods and added a K&N filter. Im ready for a turbo back exhaust and almost have enough money. So I have been looking at Buschur Racings Downpipe&Cat-back combo, and Thermal R&D's, also Apexi's. I'm kind of ify on it but i might go with the Buschur, if there are any objections as to why not to go with buschur feel free to smack me in the face hehe... now the thing that im concerned about is I plan on modding the car for a long time turbo Upgrade, Stand alone fuel-managment etc. but as for now im trying to take care of the intake and exhaust, with Buschur I have the option of a 2.5 mandrel bent downpipe&Cat-back I plan on keeping the stock catalytic converter because I'm not sure how stringent the emmissions are up here in Tacoma Washington, now I'm assuming the 2.5 system will bolt up to the stock catalytic converter, but if I go with the 3 inch system which potential wise would be the way to go. would the 3 inch downpipe and cat-back exhaust bolt to the stock catalytic converter,or would I have to get custom flanges welded on to my stock cat. I dunno this whole thing may sound stupid but im puzzled because i was on buschur's website looking at pictures of their downpipes and they didnt have flanges on their 3 inch downpipes only on the 2.5 and i also read that without porting the o2 housing and Exhaust manifold if im correct you will have a problem with boost creep.
can anyone please help me. much thanx. pz

 

[nine5raptor]

um, the cat is the most restrictive part of the exhaust and no neither will work, I don't think.

the 3" are slip fit connections