After travelling some 12,400kms on my 2020 T120 (last of the Euro 4 models) I have fitted a " Booster Plug". On the roads I ride on here in New Zealand we have a lot of tighter 2nd gear type corners on all sorts of terrain (uphill, downhill etc. ) where rpms drop back to idle or close to it as you pull up for the corner. My T120 has always suffered from the much reported bottom end flat spot and has not been nice to ride at low engine speeds and I have got into the habit of holding a few rpms on with the palm of my hand on the throttle along with a little bit of clutch slipping out of tight corners at times. After a 200km ride yesterday I have to say the Booster Plug has cured all the low rpm problems and for me at least, exceeded my expectations. I noticed the change immediately on leaving my garage and riding up my driveway (slightly uphill) , I didnt have the slip the clutch and coach the bike up the drive way with a few revs on! Im 100% sold on this device, paid full retail for it and shipping and it took just 8 days to get to me. The technical blurb on their website is a recommended read also, while its quite technical it made sense to me.
This along with a few other mods I have done to my T120 have turned this bike into an ideal ride for me ( I'm 73) as I use it for one up riding, day trips of 200-400kms and overnight / extended touring. Mods include : - TEC progressive front springs, YSS rear shocks re valved and sprung to suit my 86kg weight, 39 tooth rear sprocket, re foamed and slightly raised height seat, Dart screen, sintered brake pads front and rear (an attempt to get better "feel" not entirely sucessfull however). I have resisted the "de cat" as from what I read there is a loss in back pressure and engine breaking I understand? (as I ride in all weathers all year I prefer to have lots of engine breaking on wet days).
Trust this assists others.