hesitating

Thanks for the info Have been really busy at work and then caught a bug, so car has been sitting while I use another vehicle. However, I've since noticed a few things. The 'check engine' light is not on. There is a new and bad oil leak under the throttle body. I can see it dripping after running the car for a few minutes, but not sure exactly where the leak is. While running the engine at high rpm in park it hesitates every 2-3 seconds. Behaves same whether engine is cold or warm. Replaced a few bad vacuum line hoses, but no change in performance. Today I plan to pull parts off to get at the oil leak, then go from there, looking at the egr valve, the mass air flow sensor (maf), then the fuel injectors.