Simple exhaust question

[CrisZenithBlue]

2000 Boxster base
I had my top speed cat delete pipes with the top speed muffler and it all fitted nicely.

Went with a Fister exhaust and my first attempt to mate it with the cat delete pipes was a fail. Exhaust leaks galore.
For those unfamiliar with the fister it's basically my original stock muffler modified, but the fitting part is not touched.

I'm fairly sure I'm doing something wrong because they should mate just fine right?

With the top speed the pipe and the "extension" would be pushed together all the way. With the fister I found i had to "stretch" the two pieces to get the pipes to reach the U pipe.


Help me out people, I am doing something wrong right?

Gonna have another go at it tomorrow and hoping to hear some advices or experience.

Thanks in advance.

Cristian