Rodeo Runs Rough

A person i know has a rodeo with 120000 miles and it is running rough after adding 2 bottles of lucas fuel treatment and topping it off with Shell V-power. It ran fine before and now runs rough during acceleration. He has since ran another tank of fuel through it and changed the fuel filter and spark plugs and still has miss. What could he have messed up? I am thinking that maybe the sock filter in the fuel tank may be pugged or the injectors or the oxygen sensor. Remember, it has new plugs and wires, air and fuel filter.

What year?

1995

change the plug wires.

what kind of spark plugs did he put in it?
If he used BOSH tell him remove them and install NGK

He replaced the old bosch platinum plugs with autolite platinum. I will forward your suggestion about the NGK Plugs. What about Denso?

change the plug wires.
he did.