This may be a stupid question, but if there is a vacumn behind the first pulse, which pulls the second pulse, wouldn't the first pulse be pulled backwards, thus being redundant?
Sure it's going to slow a little, but the gases infront are moving so fast it's going to be hard to bring it to a dead stop, then reverse. Plus you still have the piston pushing up also.
That's it, if you free up the exhaust, you need better air intake, such as changing the lower and upper intakes, larger injectors and calibrate the computer for a better air/fuel level so it won't be confused.
But on a 100% stock engine, less backpressure isn't good. As for non-EFI engines it doesn't really matter or it's easy to tune the carb for more fuel. I get into arguements with owners of stock 4 bangers that put on a huge fart pipes and tells me he got 25 more HP due to less restrictive exhaust.
Engine performance is all about more air IN and OUT! Not just out!
Backpressure isn't necessare if the engine is built for no back pressure. Top fuel dragsters are built for no backpressure so they get max power from no pressure but out 5.0's need it to get max power unless it is modified otherwise