On a cheap scanner, you can watch your 02 sensors on live data. If you have a large variation, it's a good indication that it may be on its way out. Evap codes are pretty straight foward but a smoke test is the only way to tell. Also look into a bad fuel cap, it will not pressurize the system with a bad cap. I had evap codes on my truck and read that a smoke test is the only real and sure way to find it. It ended up being a nipple on the gas tank. Which required replacing the tank
. Check your intake pipe after the maf to throttle body for connection. For $100 get the test.