I had the same issue with P2006 AND p0660.. i purchased used VTCS and VICS solenoids and I haven't recieved the codes again... the codes used to pop up for me about once a month or so. Check your vac lines going to them and your sensor connections.
P0660 is strictly for reporting an electrical fault in the VICS solenoid circuit, there's nothing mysterious about it. If it's present there's either something wrong with the wiring or something wrong with the solenoid itself.
Keep in mind that P0660 does not illuminate the CEL so unless you regularly hook up a scan tool the car won't indicate a malfunction (this is because P0660 is not emissions-related). So it's very possible that the P0660 DTC is still present on your car.
yeah it does.. Unless your stock computer is completely different then mine(doubt it) then it wont cause the CEL to trip but it does trip my CEL and its literally the only code in the system at that time. Ive received both seperate and both at the same time at several different instances. The people at autozone got so used to me using the scanner that they no longer ask for my id to hold the scanner because I was getting one or the other or both at the same time constantly.