2G Stalling/limp mode P0300

[Turboed_talon_tsi]

My 96 Talon has had a bad idle for quite some time now. My car has a P0300 check engine code. Car gets warm and once you let off the clutch and push it back in the idle drops very low or stalls.

The car has recently started to go into a certain mode when driving. Not sure if it’s called “limp mode” but I think you get what I mean. Car will not rev past 2k rpm’s and only allows the turbo to spool. Goes into this mode after I give it a good amount of gas when driving.

I’ll list everything I have tried. I have already preformed a boost leak test and have fixed the 2 minor leaks I have found. I just put in a brand new upstream O2 sensor and that didn’t do anything. I pulled all my spark plugs and had them correctly gapped to around .30 +/- 2. I have not checked my ISC sensor yet. I also have an exhaust leak. My BISS screw is broken and wondering if this could be a cause. It’s still inserted down the hole but the the top part broke off. Also I have not driven the car since November until recently. Car ran meh then. Wondering if it could be bad gas? Sitting at half a tank of premium.

Sorry it’s a lot of writing, thank you.
Mods: 16g turbo, FMIC, cold air intake, headers, exhaust

 

[chrysler kid]

when you did the boost leak test how bad was it leaking out of the biss screw?

double check the throttle position sensor is fully plugged in. could have a bad connection and the car cant see the tps values

I would perform a fuel pressure test next to verify the misfire isn't caused by low fuel pressure.

when in "limp mode" will it rev in neutral like normal?

 

[Turboed_talon_tsi]

when you did the boost leak test how bad was it leaking out of the biss screw?

double check the throttle position sensor is fully plugged in. could have a bad connection and the car cant see the tps values

I would perform a fuel pressure test next to verify the misfire isn't caused by low fuel pressure.

when in "limp mode" will it rev in neutral like normal?

I don’t believe it was leaking out of the biss screw because it’s still screwed in but I’ll do another leak test To verify. I’ll check the tps and will probably test the voltage on the pins while I’m at it. I’ll check fuel too. It revs normal when it’s parked and in neutral. Only goes into that mode after a good pull. Thank you!