I have a 97 f150 4.2 v6 auto. For months the check engine light has been on. I checked the diagnostic and got a couple of egr codes. About the same time it started idling rough, almost to the point of the engine going dead, which usually doesn't, the brake light on the dash sparactically comes on and off. I replaced the egr solenoid due to low/no vacuum. I pulled the egr tube running to the exhaust manifold to see if it was stopped up. It was clear. After I replaced the solenoid I noticed a faint hissing sound like a vacuum leak but haven't been able to locate it. I friend suggested spraying brake cleaner around at potential leak areas. Also mention replacing the intake manifold gasket, these engines were notorious for leaking.What tips tricks are out there that I could try to find and fix the leak?