RE: evap leak
Ideally, you use a smoke machine to test for evap leaks. Since most guys don't have that little $1000 piece of equipment, all you can do is physically inspect fuel cap, solenoids, charcoal canister and all connecting hoses inch by inch. Bad fuel caps (or loose, missing) are the #1 cause for evap leak DTC's, but I've seen plenty of cracked lines and melted purge valves. Also see lots of stuck vent solenoids in dusty areas.