I originally bought this saw new around 1992. I did use it to do some work up in a few trees back then, but for most of its life its been a ground dwelling limber. Finally, about 2 years ago, it broke its connecting rod, punched a hole in the upper crankcase cover, and died. With the help and guidance of some good folks here, I rebuilt the engine last October with a used OEM crank and upper cover off ebay, and new OEM rings, wrist pin and bearing. The piston and cylinder still looked great after 20 years! I also rebuilt the carb and noted at that time that the high speed screw had a plastic limiter with a raised tab on it restricting the travel of the high speed screw. I reassembled it as was, but I always regretted not cutting that limiter off when I had access to it and vowed that I would do it some time in the future. I continued cutting with it all winter up till now. My opportunity came last week! I had recently replaced the 14" .063 picco bar with a 16" .050 picco bar. I got a great deal on a GB bar with "Oregon/Carlton" chain for $29 shipped off ebay (also later snagged 3 Stihl "PM" chains for it). I had only cut with it a little bit (awesome) and became concerned at the minimal amount of oil being slung off the chain. I took the bar off and ran the saw watching the oil outlet closely .................. lots of air bubbles in the oil..................... definite problem, I had a significant air leak somewhere in the oiler system! Based on the design of the 191T, I figured it was either a worn pump, or air leakage around the pump hole where the "oil line boot" fits into it. I decided to tear the whole saw down again and addressed the following issues. 1) I installed a new OEM oil pump. 2) I cleaned all the surfaces of the oil line boot and the case pump hole, and applied a liberal bead of gasket sealant (flexible, oil resistant type) to the boot before inserting it into the oil pump hole. Once inserted, I applied a little more around the outside of the joint. This dried up to a nice flexible seal instead of just relying on "tight fitting parts" to seal the oil channel. 3) I cut the plastic limiter tab off of the high speed screw to gain full range of motion and adjustment. 4) Lastly, since I could now adjust the H screw, I cut 3 additional "slit ports" in the muffler opposite the case opening.................. MUFFLER MOD! These can later be bent open more like the original 3 openings if I desire. I finished it all up last night and WOW................ does this baby CUT! The closest thing to a limbing "light saber" I’ve run yet! The "Oregon/Carlton" chain on it actually seems to cut nice, but I can't wait to wear it out so I can open my first box of old style "PM" chain! Until "MM" clarified the point recently, I never realized that the 191 has 50% more cc displacement than the 192 (46.5 cc vs 30 cc). And to think I almost got rid of this little "magnum" saw in favor of the "newer/better" MS192T. NEVER!