Hello I own a 04 Built Lightning, Look to see that it Does Not have a J code Trans, Ask if it has the Updated Intercooler ( All 99-2000's) Leaked and should have been up dated Check for a lower Pulley (Blower) Stock or over driven,Has it been tuned and by Who what is the Air Fuel Ratio, Go to Lightning Rodder.com and search this truck by Vin Number, Good Luck Lurch
I recommend checking the exhaust headers for any cracked bolts (assuming this is still stock.)
Plugs are scheduled for a swapn out after 100K. As if they have been done or not. If not Ford dealers charge between $450 to $500 to change out plugs, boots and coil overs.
BTW 2nd Gen L's from 99 to 2002 had only 3 threads holding the plugs in. Many problems with th eplugs blowing out of the head and THAT's a pretty penny to fix. This was FIXED in 03 when Ford made plug threads with 6 turns instead of three.
So unless it's an 03 or 04 then pull the plugs to see if any are different than the others and ask the question if they have been changed out or if one did in fact blow out.
I will NEVER get rid of my 03 Lightning. One Bad *** Truck,
99-02 Lightnings, Harley's have 4 Threads and under heavy boost( Plugs not torqued to 13 lbs have blown out) 03-04 have 8 thread and will still blow out if not torqued properly, These trucks are really nice but can hurt your bank account, I have put together many 10 secound trucks that are daily drivers, you can keep a stocker safe with not to much timing and a great Tune boost up to about 15 lbs is fine If tuned properly, Good Luck and have Fun,