Hi guys just wondering on whats the best set up to use with an aftermarket exhuast should i go 2.5 inch or 3 inch should it be mandrel or press bent should i use one or two mufflers any help would be great thanks mark.

2.5" is plenty big enough for a NA 6 cylinder, DEFINITELY get mandrel bends... as for the mufflers, get a straight through one, and depending on how loud u want it, u may want a resinator in the tailpipe. A lukey or a redback bolt on system should do u fine, from memory the redback comes with the option of the resinator in the tailpipe....
pacemaker extractors r the go as well...

do a search, it's covered so many times.