Have an 04 monterey 4.2 v6, drove van 2 miles shut it off, started it back up 10 min. later drove back home and 1/2 mile down the van started surging anthing over 35 mph. Limped home, changed fuel filter and took it for a test drive, drove 3 miles to store went in side for about 10 -15 min. drove home and about a mile in it started surging again around 45 mph and the check engine light came on. Pulled code P0340 which is camshaft position sensor A circuit (bank 1 or single sensor). Went and googled the code and came up with it either being wiring, camshaft position sensor or camshaft synchro shaft. Replace camshaft position sensor and cleared codes, took for a 20 min. test drive nothing wrong, stop at hardware store came out 10 min. later drove 1/2 mile the surge came back, this time anything over 40mph it would surge. Everytime after it would idle fine and rev up fine in driveway. The sychro shaft looked good and the blade was tight and their is no whining noise coming from the shaft when running. Has anyone else had this problem or have any ideas. Also the code P0340 came back on too. Runs and starts fine just cant trust to drive...

Thanks