Brett,
By 'collector' do you meant the pipe where the 2 pipes from the manifold join? Mine has a 1 7/8" pipe from there going to a short oval box ahead of the axle, then an over axle pipe of about 1 3/4" into a (rusted out) resonator and out the back.

Do I understand that you replaced all the 1 7/8" pipe with 2", and only had one muffler between the axle and the rear?

Have you any views on whether a 2 1/4" or even 2 1/2" would be beneficial? I've also heard different views on whether a single muffler is better before or after the axle. I think George (walrus3) had a preference for a box in front of the axle.

I've also heard it is beneficial to lengthen the 2 primary pipes a few inches, but can't dig up anything on this.

Regards

John