Hi Scotty, I’ve got an 02 Ford Windstar. After 35-40 mph it sputters a bit. I’ve got a check engine light on & mechanics around me say it could be the cat converter, transmission, pcv valve, spark plugs, wires, mass air flow sensor, throttle position sensor or carbon build up. It’s only got 112,000 miles & I feel like they are wanting me to throw all types of money at it. It doesn’t idle rough upon start up & doesn’t have ant issues starting up. It idles fine at stop lights and until 35-40 mph runs fine. Once at hwy speeds it runs fine provided I dont accelerate hard. Could you have any guess? Thanks for all you do!

Start with someone who analyzes them better, that's a mechanic's job, your guys seem just wildly guessing at it. I would start with a tune up then work up from there myself.