burt taste is your wick drying out (not wicking fast enough) 2.2ohm at 4.8v is only getting 10ish watts. if it is a stock coil head/ tank you may have found its limit. try a lower resitance coil head but you will probably run into the same thing. the aspire nautilus keeps up pretty good stock at 20watts and thats really the last step b4 rebuilding (kayfun would be a good jump after that)