Hello everyone I am new here im coming from s2000's so its a little bit of a learning curve. Well to start out I just picked up an 06 wrx with a few mods on it and it is giving me a fit. I am getting P0301-4 codes and it missfires pretty good. I already changed plugs even though they looked fine. I did a compression test and numbers were from 150-60 across the board. I ran an injector flush through with the pump disconnected and even swapped coils to see if it was that. Also I disconnected each injector one at a time and felt each cylinder drop. Although the idle runs higher when in closed loop it still has a miss and once it switches over to open loop the idle dips so low that it shuts off everytime. I'm really stumped as to what it could be. I was thinking it might be the cps but i took it out and its reading some resistance. Does anyone know how many ohms it should read? Well I know this is a doozy of a post but any help is greatly appreciated.
oh and also here are the mods the engine has.
3inch exhaust without cat(too dirty to read the badge lol)
thats it i believe.