Dad707, how old are the sparkplugs? They might be getting to old to perform right
How about plug wires, are any of them (especially #4) burnt, they might need replacing, u can get a set of msd wires for about 75 and it will get u about another .5 mpg
Some simple things to check first before you get to in depth
i would have left that part out..
but definitely look at the simple stuff first.. inspect the plugs, see if theres any fouling/buildup on them.. make sure the wires arent cracked, melted, or touching anything they shouldn't be(as that can cause arcing and failure to ignite the cylinder.
2003 3.8L V6 4R70W
Windstar Upper Intake with cool-air intake, MAC LT headers, BBK O/R H-pipe, and flow 40s, SCT tuner, FRPP Alum. D/S, 3.73 gears, Auburn HP limited slip, and Team Z LCAs, Eibach sway bars.
Best 1/4 time: 15.036 @90.92mph, 2.148 60'