2 barrel with stock exhaust??

I installed a SS 2bbl onto a 9.5 Scr,slanty with a small solid-lifter cam, with the original single exhaust, And as far as I could tell it was no quicker, if not slower than the preceding 8.0Scr, single barrel, hydraulic cam combo.
However I was not looking for performance with this combo, rather fuel-economy; and to that end it was quite successful.
The point is this; the stock exhaust system sux