1999 Chevy Silverado VACCUM TEST

Get a can of spray throttle body cleaner, spray the vac lines and maniflod area, when the idle changes, youve found the leak! You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs!

My service engine light came on again today and the code reads "P0358" defined as "ignition coil H primary/secondary circuit malfunction" Please tell me the part involved that should be repaired and or replaced.

Check cylinder #8 coil wire and coil for firing...plug could be NG as well.