Ok so before I start I have looked everywhere for days and couldn't find any answers. I found similar but nothing like my problem.

So I was driving under normal conditions in the city on a straight road when my car backfired and revved up a few times. And the shitty idle problem at stops. I got home fine no problems, throttle was responsive, and nothing seemed wrong. The next morning I got into car and drove from point A to B fine. As I left, the car wouldn't start. It cranked and cranked till I gave it gas. Once started the RPMs at idle were normal as well as throttle repose. So I drove off. A few min latter when I shifted into third gear it started sputtering and revving up and down. I shifted to 4th no problems there. I pulled over and the car died. Same issue with starting again but this time as soon as I moved the stick into first it sputtered and revved erratically till it died. So I put it into second hot on the clutch and took off and was fine till I hit third again. I got home. The car dies as soon as I put it in gear and now at starts I have to rev it high till it idles normal, but min later it sputters and dies. No clanking or odd noises other then exhaust.
I cleaned the MAF and throttle body it did nothing.
I hope it's just the fuel pump or injectors.
I got a barometric pressure code which wouldn't impair my driving ability from my knowledge?.. And because I drove it home like that I got p0300 random misfire. Fuel filter is new along with fuel lines. Oil is new. Spark plugs are 10k old. Half a tank. Only mods as of now is zzp CAI and cat-back.

Any ideas? Because I don't want to spend a fortune at dealer if I can do it.

Thank you

 

What codes does it have now, just p0300?

 

I should have mentioned it went away. So at the moment no CEL or codes.

 

Check your barometric sensor value to the computer, that is your problem....

 

Will do. Thanks.