1995 Ford Windstar exhaust system problems

Exhaust system has corroded, and is causing fumes to enter vehicle while driving. Dealer notified. Oxygen sensor failed twice and was replaced. Head gasket failed and was replaced; also the internal leaks from head gaskets in vehicle corroded flex pip and exhausting into vehicle. Engine failed and was replaced. The outer right and left tie rods failed and were replaced. Air filter failed and was replaced. Pcv valve failed and was replaced.

I have a 95 ford windstar (89k) LX3.8; DTC p0306.... Gave rich condition, black smoke out tailpipe, excessive fuel consumption ... Don't stay running. Spent more than $4,000 on the repairs didn't resolve the problem. - have replaced all o2 sensors; - have replaced spark plugs/ wires; - have replaced starter/ battery; - have replaced all the upper intake gaskets and intake isolator bolts; - have replaced the fuel injector #6; - have had replaced all water pump/gasket, A/C and transmission two years ago still didn't…