Was it hard to tune? Not hard if you have proper gauges and logger
How often do you have to refill tank? small 5# tank normally lasts 3-4 gas tank fill ups and costs $2.50 to fill
How much did it impact O2 level? It is an additional fuel source so your O2s will richen, you will need a fuel computer to pull some fuel to get back to normal O2 levels
What boost could you run with minimal knock and timing pull before propane? Our numbers and numbers from many others running same pump gas b4 propane and after propane you can gain average 4-6 psi without knock
What is your timing and knock now at high rpm's in 3rd at 20 psi? I think that is better answered by a DSM guy, our numbers are not DSM specific
What is the highest boost you can run now without timing getting pullled below 15? again, I think that is better answered by a DSM guy, our numbers are not DSM specific