Misfires in 4'5'6 are your vacuum leak. You're running lean on high vacuum pull. Ya gotta fix the leak right, no duct tape! Don't drive until this is fixed, as you can cause real bad stuff to happen (comic book version lol)
The clutch code is probably the clutch connector (red colored) - it senses clutch engangagement during running and is tied into cruise control.
The 0638 may just be that your e_gas needs to be calibrated. I think there's a procedure for it in the owners manual somewhere. If not, I found this one posted somewhere in the interwebs.
Let us know how things turn out!
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