The '94 has started to lose power, on occaision, usually on an uphill grade with a full tank of gas. The check engine light comes on, you flutter the accellerator and it goes out and the power comes back. The MAP sensor tests good, as does the fuel pump. If either the Mass Air flow sensor of the MAP sensor is bypassed it runs like something my horses can outwalk. The only code it has registered is "fuel lean". Any ideas? Thanks.