Ok dustind and guys, my impressions after installing both eliminators are very positive
The response is greatly improved in almost every condition, especially when riding in the city and after slowing down and accelerating again from high speeds on the highway. The engine feels fuller and the running is smoother especially when the three first gears are engaged. It's also more pleasant to rev the engine higher and the backfiring is still there, only slightly muffled. The noise has also changed a bit overall. Thanks to the o2 eliminator the bike runs smoothly and stably below 4000 rpm without any variations, so I guess this would be a cheap and effective way to fix the low rpm roughness due to emissions regulations when riding in the city that we heard of so many times
, even with the stock exhaust!
From what I saw, the pair valve mechanism (about as large as a pack of smokes) that is now no more on the bike and the accompanying tube form a quite large hole which is now closed and not creating a hollow sensation any more. Also, the easy way to block the pair valve with a marble leaves the sensor active and still sending signal to the ECU which doesn't seem right to me.
The packaging was good and I got both products within two days.
Overall, I would very much recommend both eliminators as they seem to offer improvement at a relatively low cost!