1978 KZ650B Carb Issue

I recently received a 1978 KZ650B that was in top performing condition in Texas. A few days later it was delivered in Denver, CO (5000 ft elevation gain) and the bike wasn't running so good. There is about 20,000 miles on the bike. It wouldn't idle efficiently (I had to constantly adjust the idle screw to keep the bike running) and the mixture was very rich (black plugs, full of carbon). I found that the needle setting was at the 4th position from the top and I reset it to the 2nd position from the top in order to lean it out. I then received info from a local mechanic that because of the altitude I should reduce my main jet by 10% from the stock size. My understanding is that the stock main jet is size 102.5, so I dropped it to size 92 (the main jets that I removed didn't have a size stamped on them). I cleaned the carbs and ensured that all the jets had clear passages. A mechanic from Texas where the bike came from recommended moving to hotter plugs to burn up excess fuel, so I replaced NGK B7ES plugs with NGK B6ES plugs. The bike seemed to start and idle better after making these changes. I adjusted the air screws from the default of 2 and 1/4 turns out to 1 and 1/4 out to get the smoothest idle. The bike doesn't seem to be responding in the mid to high range when I open the throttle. There is a very big lull and loss of power. Please give me any thoughts or tips.

Thanks,
Ryan

To your knowledge does your b2 have the stock carbs on it. IIRC that year they were vm24ss. There are some models that came with vm22ss which had a smaller main (97.5) Have you used a magnifying glass to look at the orginal jets, sometimes the numbers are very very small. It would help to know what they orginal ones are.

In general, if the engine is having troubles at low rpm (idle to 1/4 throttle), the pilot system or slide valve is the likely problem. If the engine has problems between 1/4 and 3/4 throttle, the jet needle and needle jet (most likely the jet needle) is likely the problem. If the engine is running poorly at 3/4 to full throttle, the main jet is the likely problem.

Since most riding is done in the mid throttle area it needs to be corrected first. I have attached a document, I did not create this guide so am not taking credit for it, and was told it was from an article by Don K. Courtney. I have found it very useful in my tuning.

Sorry it did not post the attached doc so here it is