Hi,
Yes, time and experience does help. In answer to the metering rods, they can be changed to fine tune mid-range response. They are available in leaner and richer stages, all else being OK. Edelbrock tuning manual has a section lists kit numbers and their AFR affect. However, knowing which way (leaner/richer) to go is the "key".
My best advice for anyone wrenching on their rides, is to keep a log of all changes in detail. Also, don't make numerous changes at once as the affects can not be determined specifically.
Good Luck!