Tight on money, mechanics here in San Diego have been booked up for weeks, so have tried replacing a few valves to solve a check engine light -P0401 - car is running much better, but still getting rough idle at times and check engine light has not reset after days of driving. Motorcraft EGR valve was about twice the price of the Standard brand one from Oreilly - what has been your experiences on the quality of Standard brand ignition parts?