I have two codes and am not sure where to start or what they exactly mean.

P1590
&
P0308

Where do I start?

Help is appreciated.

 

They aren't related. From the P1590 I assume you have the 3 Amigos lit up.

The other one is a cylinder 8 misfire. When is the last time you changed your plugs and wires?

 

The amigos haven't lit up just the SES light came on and the wires are STI and plugs were done last July.

 

I am guessing i need to check the spark plugs? also, This morning i come out start the truck and drive to the office and no SES light at all? What am i missing?

 

Yes, you need to make sure your plugs and wires are in good shape.

You aren't missing anything - if the motor goes through enough cycles without a misfire it will clear those codes. So what it sounds like you have is an occasional misfire. Could be weather related (humid/wet) or something similar.

I'd suggest pulling each plug and checking it for gap and condition, and pulling each wire on both sides, check the entire wire and both connectors for condition, clean the connectors, and put a bit of dielectric grease on them before refitting. That heads off moisture problems pretty well.

If you find water/oil/gunk in the spark plug holes, you probably have a valve cover gasket leak. That's a good way to get occasion misfires. But don't despair....most times that can be handled by simply pulling the intake off (easier than it sounds) and re-torquing the valve covers properly.