HELP!!!! 1994 Jeep Wranger 4cyl. Bogs down, have to lift up on the petal and punch it again. Then bogs down again. Will kill it if i keep my foot on the gas. Downshifting helps sometimes. Happens mostly on highway driving. Also, air filter is oily, and where the airbox mounts to the throtle body is oily. apprx 148,00 miles. Whats wrong???