My truck is now at the Dealership and they cant figure out the problem. My engine light is on and has been for awhile. When they hook it up to the computer it brings up a code that reads Large Emissions Leak. Parts I've changed, Thermostat, MAFS, Cap, Plugs, Wires, temp sensor on block, and a solonoid that has a green cap on top that says hand tighten only thats located next to the air intake ontop of the motor. The dealer cannot figure out the problem. I told them the engine light has started to flash then goes steady. It has also started dogging on me, which feels to me like the brakes are comeing on. Please help

---------- Post added at 04:02 AM ---------- Previous post was at 04:00 AM ----------

I've also replaced the gas cap several times and now I'm back to a stock cap, the rotor has also been replaced.