Hesitation and rough idle

My truck has a straight six cylinder engine and it recently developed this problem to where its runs too rough or rich and I can only get about half throttle before it starts to bog down and almost stall, also when I am coming to a stop I will take it out of gear and coast to the light or stop sign and when that happens the engine almost stalls and I can hear it just revving erratically.

I changed the distributor cap and spark plugs, air and fuel filter and the throttle position senor.

I am about to look at the oxygen sensor but I want to find out if someone else has any advice before I start pouring money into it.