I have an 02 Chevy s10 4 door crew cab pickup 4.3L that has no EGR. Check engine light has been on for months and cannot figure out what the problem is. The code says too lean bank 1, bank 2. Have changed 02 sensors, MAF sensor, all 6 injectors, fuel pressure regulator, upper and lower intake gaskets, new fuel pump, full tune up. Chevy, my mechanic and other reputable shops can't figure out what the problem is. Any ideas, suggestions, anything at all?