2010 F150, 4.62v, been battling lean,rough idle issue for some time, but long story short,here is my question. Has anyone noticed if your idle drops when you apply your brake ? Warmed up, in P, normal idle sits around 6-700rpm. IF I put on E brake, put in D and allow it to hold on E brake only the RPM holds pretty steady. When push the brake pedal, the RPM drops noticeably, to 500RPM or lower and rises when I let off. This would seem to indicate either an issue within the booster itself, or a borderline amount of manifold vacuum at idle, which is not enough to supply the booster. And yes, I have been all over every hose, fitting, PCV valve etc under that hood at least 3 times recently and using all the usual methods, WD40, throttle body cleaner,smoke and even was desperate enough to try ether (cold engine start up mind you) in an attempt to find even the smallest leak. I even just replaced the upstream o2 sensor , drivers side, based on recurring engine light and code. I seem to feel that the issue still remains and that sensor was a waste of time/money, as the idle is still rough at it's lowest, especially with the AC on. You may not notice it as a passenger, but as the driver who has put all 142,000 plus miles on her...I notice it and it's different than before. Plugs are new platinum, couple months old..MAF replaced about 6mos ago, throttle body cleaned regularly (I'm a maintenance freak) Just grasping at straws for ideas to try next. Any and all help greatly appreciated !