New to the 4.6L mustang

I have a 2002 mustang GT automatic and in drive with overdrive off mine idles at about 600 RMP I don't have clue if anyhting is wrong with yours it could be that it just needs a tune up.
hope this helps.

Welcome!

Look up in the sticky section for the mods list. It can def point you in the right direction to stay n/a. Looks like your well on your way. Most stage 1 cams are real easy swaps, some don't require spring changes. Stage 2's usually do.

The idle could be multiple things. Check your t/b and see if its stock or not. It should have an idle adjustment screw on it.

To set your idle. First unplug the negative terminal on the battery, then go press the brake pedal for 30 second (this clears the kam memory in the battery as it has a back up)Hook batt back up. then unplug the iac on the front of the plenum. Start the car. Set the idle to where it is just BARELY above where the car stalls (this may take a helper to keep the car running) Then turn the car back off one you have the set screw right (remember to try to not touch the gas at all during this) with the car off, hook the iac back up and see where the car is at. ** remember to do all of this with the car at operating temp b/c it will be a bit different idle on a cold motor.

Good luck and welcome again.

where are you at in hagerstown?

try to clean the MAF... might help the idle might not. if its dirty it can cause a few things with the idle.