I have used Throttlemeister on my late-model K bike as well as an 'olde' Airhead. I managed to modify one to fit my K100RS with the hollow handlebars. I like the way it works. I set the tension just so, never locking it fully, to relieve the mild wrist aches on The Long Road. I recommend them. Of course, a rubber band or thick rubber o-ring jammed between the throttle tube end and the throttle housing will do something similar and you'll save a fair bit of dosh too! An added bonus with the heavy duty version of the T-Meister is that it is a high frequency engine buzziness killer as well.
At the other end I had just this week received the excellent Motad round stainless steel silencer from Motorworks UK. It is not intended to be a 'performance' exhaust but with a slightly more raspy note than my old square cannister it feels like it gave me a small seat of the pants push up the power curve. It is fiddly to the point of aggro to fit, however. I imagined a couple of hour stint in my garage...at half past midnight I was cleaning up my tools to retreat to my comfortable bed. I had been there for over five hours! The header to silencer is a tight slip-fit using no pinch clamps as the OEM exhaust does. They're tight for good reason; they need to properly seal and not allow exhaust leaks. But this exacerbates the problem of trying to get all four moving headers to align with the silencer, even with lube to help them slip together. A fair bit of gentle pounding with a soft mallet is in order.
In the end it is worth the trouble. The Motad muffler is shorter than the stocker, clears the panniers no worries, looks better, is tidier, and at 4.5 kilos in total as compared to over 7 kilos for the stock system. One thing I've noticed too is that the engine's slight buzz used to fall in the 3200 to 3500 rpm range and it is now at the 3000 to 3100 rpm range and no more. I suspect the stock exhaust's vibes might have caused some of this mildly annoying buzz.
I ordered it from Motorworks UK because it was listed at just under AU$700.00 from the Melbourne distributor and was only about AU$375.00 including freight from the UK to OZ! Their service was very good with frequent correspondence and an online parcel tracking service at no 'extra' charge. BTW, Motorworks do not advertise openly on their website that the exhaust is the aforementioned high-quality brand I received...nudge, nudge, wink, wink.