Car trouble 1996 Ford Tarus running on 5 cyclinders instead of 6?

1996 Ford Tarus Wagon , 3.0 Duratec V-6 Dual cam . It runs on 5 cyclinders and backfires inside intake manifold and sputters ,bogs when accelerated especially up hill . Stall at stop lights and hard to start again . Smells of raw gas all the time , when started and while accelerating . U can hear liffer noise on back side of motor click ,clicking I tried taking off intake manifold ,got all nuts and bolts off ,linkage and hoses and still couldn't budge rear part ,seemed like it was anchored on back there by something I couldn't see or feel ?. There is also oil in butterfly housing . Any suggestions?.