[undy]

I agree whole heartedly with the idea about not wasting money on a high $$/HP engine if you can't make the horse power materialize at the tires. That's why on the intial dyno I did a before 'n after with the side pipes (and the air filter too..no difference there). Merge collectors/equal length primaries/stepped primaries etc, etc are all important too. Once I get the back pressure right via a better flowing muffler design and regain 80 of the 100 HP I can then spend some more $$ on Merge collectors, trying to get another (maybe) 15 horse power. The vast mojority of our power losses are due to restrictions aft of the collectors, IMHO..