Tunes dont just magically go bad. If it was fine before and now something is wrong there is a mechanical part that is broken somewhere. Its more the plug wires than the plugs, but since you mention they are so hard to get to I am leaning more that way now (burned plug wire).

 

Yea maybe one of the waited moved and is touching the header I guess it's time to do the night time rest and look for the spark.

 

Yep - sounds like it to me. Have had this happen twice - once when the LTs where put on and #1 plug was cracked and recently when my 2 of my supposedly extreme high-temp and costly Granatelli wires gave out (even with a boot).