I've known the problem to be intermittent on both my dad's and our srt. I suspect the water temp spikes and it cuts the supercharger, then it might cool down enough to re-set to normal operation. Or possibly the pump itself works intermittently due to some internal problem. Whatever the cause, the symptoms worsen until you have boost only when the engine is cold.

Both of the rockets under my care are getting new pumps from needswings this weekend. They seem to last about 36,000 miles, whether Johnson or Bosch.