Ive heard from others it is normal to have a little pressure release, but when I take my gas cap off I get a pressure release that is not what I would consider to be "little". Is this a fuel system thing or something else? Also when I let my foot off the gas in 3rd -5th gear, I hear a popping coming from my exhaust then when I give it gas again it pops right when I let the clutch out. Could it just be backfiring, or something else? Maybe my injectors need cleaning? Sorry if this has been asked before but I couldnt find anything about what I am experiencing anywhere else on the forum.

 

your first question is it is normal. with warmer weather the pressure is greater.
As the popping is the exhaust leaking? Is it aftermarket? You can always throw a bottle of injector cleaner in your gas & see if you notice a difference.

 

Any CEL codes?

Pressure: The high pressure in the gas tank may indicate a malfunction in the EVAP system that collects fuel vapor in the EVAP canister under the hood.

Popping sound: If the exhaust sound is not abnormally loud when accelerating, then you may want to do a tune up and check the ignition timing.

 

Backfiring is not normal for a fuel-injected car. When you release the gas pedal (above idle speed) the ECU should cut the injectors off completely. Check the TPS with a voltmeter.

 

This would also lead to a high idle speed, in which case an overly tight throttle cable or dirty throttle body should be considered.