Hi Yamablue,
Greetings from Manila!
I do have a US version AND an SR version of a KDX, but they're both 250s. The SR is a 1992 (F2) and the US version is a 1993. Like your SR my SR has a small carb, 32mm vs. 38mm for the US version.
I'm not sure about the 200SR, but my 250SR has a different power valve set-up than the US version. The SR only has the two side valves while the US version has the two side valves and the main "center" valve.
The US version definitely rips compared to the SR, but remember the SRs were manufactured to be street ridden, too. They are more mildy tuned. In fact, a US version piston will not work on the 250SR version even though they have the same bore AND stroke. The wrist pin location is different.
I have recently spent a good bit of time jetting my SR correctly. It came from Kawasaki with a 148 main, a 42 pilot, and a #5 slide in the 32mm Keihin. I put in a set of Boyesen reeds, and finally settled on a 142 main and a 38 pilot, with the clip in the top (most lean) needle position. She runs quite nicely now, pulls like a tractor off idle and will run out very nicely on top. I'm quite happy with her now, for a street legal dirt bike that is!
I don't think the snap that you're looking for will be found by trashing the oil injector. You have to face it, your SR version will not run like a US version without swapping some parts, bigger carb, cylinder (if your SR only has two power valves), etc. etc... and make it an US version!
I ran a "test" to check my gas-oil mixture once on my SR... I made sure the oil pump was adjusted as per factory specs, topped off my gas tank, added my 2T oil until it filled the tank, and went for a ride (about 75 miles). After my ride, I filled both my tanks to the same pre-ride level (measuring the fluids I was putting in) and I came up with an average of 68:1 gas to oil. Interesting...
I love my SR, it is smooth and mild on the street and still offers a good ride when the pavement ends! Maybe hang onto to your oil injector, get your jetting right (if it's not already), and add a set of reeds. If you need more snap than that affords you... get a US version and be done with it.
For what it's worth... stay in touch, fellow KDX SR owner!