I guess what my dealer says is the problem with the zards is back pressure, or lack of. It takes quite a bit of tuning to get one to run nice. Your original ECU cannot be mapped. To use a rapid bike or something similar you need to get a DP ECU. I got one used for around $400. You can pay as much as $1200. You then need a rapid bike or similar, $400 on up. Install and map it. Another $400.
Or you could also get a nemisis replacement ecu. $1200 plus install and mapping. That is your best option.
I want zards on my bike, but the dealer keeps making sure I understand how much I will spend to make it all work proper. Sounds like your dealer didn't prepare you for what you were in for. I will get zards one day, I'm kinda waiting for someone who is frustrated with theirs to sell them cheap. My plan is open airbox, nemisis ecu, zard exhaust. Oh and lots of dyno time.
The first thing to do is to check the joints for leaks in the new exhaust system and seal them up.
Backfiring is the sound of fuel being burned in the muffler. To happen, you need unburned fuel, an ignition source (hot metal, exhaust gases) and air. When you quickly chop the throttle and decellerate you send the greatest amount of unburned fuel to the exhaust and this is when the condition is the worst.
An unburned fuel condition is usually caused by a lean condition. What happens is that a lean mixture will fail to ignite consistently. This, in turn allows some un-burnt fuel to get into the exhaust pipes. Then when the engine does fire, these un-burnt gasses are ignited in the exhaust pipe, causing the backfire.
Any EPROM chip or Power Commander fuel map that is not well-matched to the exhaust system can produce an air/fuel mixture that results in more unburned fuel being sent through the exhaust pipe and muffler. So a chip change alone can cause backfiring, especially during closed-throttle deceleration.
The best approach is to put the exhaust cans on and have your dealer re-adjust the CO level to compensate for any increased airflow. There's a CO trimmer screw adjustment on some ECUs that provides for limited changes in fuel mixture at idle (with lesser effects across the RPM range). Go easy, a half-turn on the screw is usually all that’s needed. Any more may decrease drivability.
Always a good measure of fuel mixture is to check the color of the inside of the tailpipe. After a few hundred miles it should be medium-to-dark gray, not black or sooty.
Slip-ons as a rule won’t change air flow very much. The most common situation is that a newly-installed exhaust pipe or slip-on is not fitting properly. Aftermarket pipes are not a precision fit and often they let in combustion air that, when mixed with unburned fuel, results in the fuel being burned in the muffler. If this is the case, use a high temperature silicon sealant at the joint to the slip-on to keep the air out.
Full length, larger diameter exhaust systems are designed to flow better so more air through the valves without added fuel will usually give you a lean condition. You need to check the air/fuel ratio on a dyno to be sure.
I recommend Permatex Ultra-Copper high temp RTV silicone gasket maker #101BR for the aftermarket slip-on system joints. Good to 700˚F intermittent. Available in auto parts stores.
I run mine with a DynoJet custom map from Orient Express. The bike is a completely different animal even from when it was stock. No more jerky throttle at low RPMs and definitively no more popping sounds on decel, Just awsome! Well worth the investment
@papawheelie: just for your info, with a RapidBike module, you do not need to have a DP ECU. I have a GT with stock ECU (and working O2/lambda sensor) with Marving exhausts, to which I coupled a RB3 module.
The FatDuc will most probably not help here, since I guess you are interested in running the exhaust system without the baffles. And with so little back-pressure, you have to remap across the complete envelope. With the FatDuc you can manipulate the signals from the O2/lambda sensor going to the ECU. Just modifying the fuelling down below 4000rpm (with the FatDuc; where the ECU "listens" to the O2/lambda sensor) will still result in a wrong fuelling above 4000rpm.
If I were in your position (which I was some time ago I'd consider a RapidBike or the Protune suggested by moto.