speedjunky is correct. The knock sensor is broken in half. half is in the block and the clip side was broken off in the plug that is just hanging.

Also the car received a valve adjustment the same day, could this be the problem?

 

When they removed the valve cover for valve adjustment, did they remove any wiring on the firewall there? Also, check the ground on the back of the head, very hard to get to, you'll need to go by feel, it's between the head and the firewall. If it's loose, you'll have all those problems.
Get fuel pressure checked. Like, fuel pump may be on its way out, especially if at that time you're low on gas, a bad fuel pump will heat up more, and not provide the needed pressure.

 

Ill check the ground. But it I have checked the pump and that appeared to be good.

 

A faulty knock sensor will put the car in limp mode.
Shouldn't affect the car running at idle though.