I was under the hood changing out the fuel and air filter, started truck and had a weird tap sound, if I put my finger on the 1st injector line it has a real hard tap, none of the rest do, what is this, should I worry?

 

Don't worry, this is normal for 3rd gens. That #1 injector line does not have a support like the others and therefore you can feel the injection pulse.

 

thanks, I was looking at that just now and put a small aluminum block to kida hold it and it is still there, but not as bad

 

I get a tap with my '03 until the temp gets up a bit.