Decel Popping with Hooker Pipes

I've got a '05 Softail Deluxe with a Stage 1 Kit and a pair of Hooker Step Tuned Classic Stagger Duals with no baffles. I took it into my Harley Dealer and after they put it on the dyno with the race tuner it has started decel popping in every gear. They say that the fuel/air mixture is right on and there is nothing they can do. They checked the exhaust gaskets and there is no leakage. Will a set of Hooker mullers or a tuning core help or is it just running too lean? Any sugggestions would be greatly appreciated.

The HRT is flexible enough for them to richen up the mixture some with the throttle closed.

It is not the pipes it is the mixture causing the problem if it is decel or lean pop.

The dealer may have the F/A ratio right on the money on a wide open throttle run but, unless he can load the bike at different throttle positions they cannot set the F/A ratio at every throttle position very easily.

The Dyno Jet Dynos with the dynamic load device allow the operator to keep a bike at a given throttle position to get the F/A ratio right. The problem with older Dyno's like we have is that they are good for tuning but it is much like the plug chop method. You need to make multiple runs and read plugs and look at the runs for indications of what the mixture is. Holding a bike at a certain throttle position without a load is a PITA.