By suggestion of someone a while back on a post I decided to pick up some NGK Iridium spark plugs. I was told at the time to get TR55IX plugs. I ordered them online (only $43 for 6). BUT, after more discussion, I was told to get TR55-1IX plugs. WHAT IS THE DIFFERENCE? Am I going to hurt anything by putting the model I ordered in? Is there a disadvantage to it? I did extensive research and found that there really are two different part no.'s...I also contacted the place I got them from and they said NO RETURNS. Should I still put them in or will that be a bad thing? I REALLY want to replace those damn autolite coppers that have been rotting in there for the last 14,000mi or so...