Its a shame that your dealer has to resort to idiocy when he is at a total loss in the tech department. Your pipes aren't causing your wobble, and neither are your neck or wheel bearings.
Aftermarket pipes may cause your Stapes to wobble (inner ear bone), and they might cause the blue light to wobble on the fancy car behind you, but they won't have any effect on handling, even if you mount them backwards!! HAHA!!
Loose neck bearings are pretty obviously found just by jacking the front wheel off the ground and moving the forks fore and aft. If you can't they aren't. Worn neck bearings will create a "detent" in the turning radius and actually work to PREVENT wobbling. You get the weird sensation that the bike always wants to point directly ahead.
Worn wheel bearings will talk to you, and poorly aligned wheel bearings won't allow axle installation, so rule them out too.
There are three major contributing factors to front end DECEL wobble on the LC, and it is not at all an uncommon issue. (your dealer doesn't know about it because he is accustomed to using really stupid excuses for his lack of knowlege, instead of doing his homework).
1.) Rake & Trail. This is the physical relationship of the frame, neck angle, Triple tree depth, fork length and axel placement. It is NOT adjustable, and never changes. The LC has a rake and trail equasion that pushes the limits of good handling. We like that long, extended front end look, as opposed to the straight down look of stuffy touring bikes, but it comes at a price. Handling.
2.) Bridgestone tires. Ever notice that wiggly center tread running the perimeter of your front tire? Sucks!! Especially when you let off the gas and your bike naturally puts more pressure on the front tread. Its a shame your dealer didn't at least think to offer you a better handling tire as a replacement for the OEM. I have often said that if you want to dicker with your dealer on a new LC, forget about savings, and make him change both tires to Metzlers before you ever pick the bike up! Now, forget about what Suzuki says about tire pressure and put what Bridgestone says put in the tire. Anything less than 32lbs is going to allow that wiggly stuff too much bite on the road. Your cupping on the old tire was due to two things, low air pressure and the nature of that tire. The Bridgestone tire has a hard center band (the wiggly part) and a soft cornering band, and naturally, the cornering band will wear away faster than the center band, leaving not only a cupped tire, but a sharp "V" profile, which becomes a stark contrast to the flat profile of the wearing rear tire. This opposite shaped wear pattern will also cause your bike to oscillate in the curves as you get in the 6-8000 mile wear range, and it stays that way until you replace the tires.
3.) Weight distribution. A lesser issue, but works in conjunction with rake and trail and tire tread to create poor handling issues at times. Not much you can do to change the natural weight distribution of the bike and rider, but use extra caution when loading the LC up for long distance riding.
Even when all is right with the world and bike parts, the LC will still have a noticeable decel wobble if you release both hands from the bars. If only light grip with one hand stops or prevents the wobble, then nothing is wrong with your bike, but you really should consider Metzler 880 tires for your next round, or Dunlops, both better handling tires.
At best, you might be able to talk your dealer into a decent discount on a different tire, but I wouldn't count on it. His ignorance has shown at your expense, and that's a shame, but it ain't illegal, so there ain't much you can do.
Keep the front pressure up, tighten up the rear shock if you haven't already, and start saving your pennies for a GOOD set of tires, and in the mean time, keep both hands on the bars when you're slowing down!!
