After looking further into this, the entire discrepancy was from the lack of a check valve on the Preludes. It seems I was in fact describing the operation of the secondary intake runner flapon the car, and had discounted the effect of the check valve until you posted that nice picture. I now concur with your system operation. Still think we went a little overboard on the callouts, but at least we can put the flapper to bed now. And rightfully so, as that was the longest discussion I have ever had about a part that neither of us use, lol.

 

Yes... they put it on there to conform to emission standards, all this system does is replace the need for a catalytic converter, It basically just adds fresh air to exhaust fumes to give a proper emmissions reading, why do you think people take it off? There is a diagram online somewhere that shows in detail. all the pair system is, isa valve attached o fresh air houses, that opens and closes to mix air in with the exhaust. which ideal gives a proper air to unburt fuel mixture within the exhaust port toignite and burn off the fuel. by removing the pair system all you create is richer exhaust fumes.there for is a lean condition is created in the engine it would cause popping and backfiring,

 

Running rich causes the popping. The guy already came back and said he was running rich. Running lean is the cause of a backfire, but a backfire is when the combustion is slowed to the point of going back out the intake ports. Remember on old cars when the flames would shoot up out of the carb if you tuned it too lean, thus the term backfire? The popping in the exhaust is not a backfire. It is supposed to do that to an extent, he just had a full exhaust and could hear it much more. It's a common thing to have to tune the bike to get rid of the rich condition that Honda gives the bike from the factory.