You have a lot of different sizing there....which will probably create some exhaust flow turbulence....you don't want that....

You have two choices....

1. Go with the same size the whole way back....example; 2.5" header, 2.5" cat, and 2.5" catback.

2. Increase or have a "stepped" design....example: 2" header, 2.25" cat, 2.36" exhaust.

I wouldn't recommend different sizes throughout the exhaust system like you are planning. But that's just me...

Sometimes when people just throw parts on and they don't worry about sizing, they don't get the results they were expecting, and they find they've wasted a lot of money. They learn their lesson though. Good idea asking first, that's the first step to learning. =)