Help installing apr dump pipe to oem catback ?

[Magoo]

Hi all,

Just purchased a APR Dump pipe/cat from a forum member.

I have read that if installing with stock catback trimming of the dump pipe is required? Is it at all possible to trim the oem catback instead?

I would prefer to not modify the dump pipe.

Cheers A

Note - exhaust does not have a 3"-2-5" reducer, I'll require one right?