There are too many things that can cause this issue. All you are going to get is, it happened to me and it was "XXXXXX"

IMO step one is to make sure all the maintenance is up to date. Plugs wires filters, re-torque the intake, look for cracked vacuum hoses, clean the IAC motor (assuming you have one, you never said what engine or year) clean and test the EGR valve.

This is all just maintenance that should be done to every car.
Note:If the car need plugs keep the old ones and mark them as to what cylinders they came out of, it may help if you have issues once the maintenance is done.


Once the above is done and you still have an issue you should do a fuel pressure test to check the regulator and a vacuum test to verify the condition of the motor and then hook up a scanner so you could see what is going on. You will need one that can read sensor data.

 

which vacuum line did you find with orange in it? post picture please.
what did you torque the heads to?
did you replace the head bolts with new ones?
did you find a failure point in any of the gaskets?

 

i have merged two of your threads so the history of the car and issue is easier accessed