99 mustang v6 p1309

i have a 99 mustang v6.when i first got the car it idled very rough and low. i replaced two oxygen sensors,idle air control valve,egr valve,coil pack,and even took the intake off to ensure i didn't have a vacuum leak.it idles ALOT better and has more power but now i have a code p1309 which says cam sensor or synchronize cam sensor.when i had the intake removed i also had my mechanic replace my timing chain,in order to do that you must synchronize the cam sensor.ok, so after that came the code, and he said it was the sensor itself, so i replaced it and the code came back a week or so later. by the way i did not just start replacing parts, each part that i replaced either had a code for it or i had it tested and found out it was bad. please help me i am running out of ideas and money.also it idles at 800 in park,neutral,or reverse but idles at 700 when in drive? is this normal??