Hi John ....

Yes to all your questions .... I currently have a single downpipe manifold on the car and it goes into the 2" pipe at the end of the header pipe. When I put the dual downpipe manifold on I will probably have a dual headerpipe built with a 2" collector .... as far as lengthening or shortening the collector goes .. I once read an article which stated that that will tune the exhaust to be more responsive at certain RPM ... but it was so long ago that I read it I really have not got the reference at hand ... like we are talking the 60s ...

You might find something on the net ... perhaps if you do you can post the URL ... it might prove to be something interesting to play around with .... actually changing the diameter of the pipes should also change the resonant frequencies of the exhaust flow too ... I guess it just boils down to whatever works ... just get rid of that VERY restrictive stock size pipe.

Many years ago I had a Triumph TR3 and I installed what was supposed to be a Volvo muffler on it .... it was rectangular with the corners bevelled at 45 degrees ... quite heavy metal .. was about 15" long ... sonded GREAT on the TR ... would love to find another one of those ... might have been a resonator .. but that was all I ran on the TR .. wasn't too loud ..... but sounded great.

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Brett Sutherland & the 1.5 million mile 122 Canadian