Hey Guys,,I just modified the opening of the exhaust tail pipe on my Milltek..And it still retains the stock tip.
I opened it up to the 2.5 '' O.D.diameter like the rest of the pipe exiting out of the muffler..Milltek has it stepped down to around 2.200" OD for about 1.5'' length to fit the tips.
I took the tips off,then used a Lisle tool #34400 tailpipe expander which worked great in the pipe.It only expands to 2 7/16'' ,so you can not over expand it..
You have to take the spacer/swivel ring out of the tip body and discard it.
Then use the same Lisle tool to open up the tip body that slides over the tail pipe.
I used an electric impact for the tool...Also spray the hell out of the securing tip bolt becausce of the rust and if you can heat it ,else it might brake like my first one did..
Now you have a true 2.5'' pipe and the internal piping in the muffler is 2.75''..
It does sound a tid better/louder,should help on power?

 

Next I might try replacing these massive HJS 100 cell cats by getting a cat delete pipe fabricated,,Even though HJS says these cats flow enough to handle very high HP applications?