Magneto gone bad? They don't last on R22 as they are exposed to too much heat. You are getting radio interference as well? Good indicator that something is amiss.
Close monitoring of any trends in MAP at 100% RPM and flat pitch can tell you lots of things. Compare the MAP required to maintain 100% on L to R. Good indicator of general health of the engine. Obviously the lower the MAP the larger the power margin you may have - generally. Also can be an indicator that your "flat pitch" might be in the ballpark as well. The more "efficient" the engine is the less throttle opening (MAP) will be required versus a fixed load to maintain 100%.
Also check your mags before "every" takeoff not just each flight. Saves you from flying around with one when you think you have two.