possessed tach and engine surging

hey got a lil issue here im trying to understand and needed some other opinions. When I come to a stop at a intersection or stop sign my truck will start surging and dying and occasionally will stall. As of now no engine codes and a simple touch of the throttle and the surging goes away. one thing I have noticed is that my tach jumps from normal to zero whenever it feels like and will bounce in between like it is possessed. I have my opinions on what it could be and I believe my crank pos sensor is ting on but that's just a guess without codes. any help would be greatly appreciated.




99 Cummins 24 valve-Edge Juice w/attitude-100hp nozzles-banks high ram intake and boost tube-4 in straight pipe-