engine stalls at low speeds

What is your question?

I have a 4.6 V8 1999 Ford f150 manual transmission 4x4. It has 85,000 miles. I am the original owner. Traveling at 75 mph or other high speeds you wouldn't notice anything wrong. When you slow down to stop or down shift the engine stalls and stops running. It starts up with no problem after this occurs. I changed out the pcv valve, but that did nothing, it had the original and the book says not to change it until 120,000 miles. I use a K&N air filter and it is clean. My next guess try the fuel filter, its been replaced at least 4 times during the life of this truck. Any suggestions would help.