Yea, the 270cc isn't enough. The ECU is sending the signal for a 370cc injector. So you are getting 27%less fuel than normal for that cylinder. ITs a lean cylinder right now. Def get another 370cc ASAP.
www.heavythrottle.com sells them.
All KA24DE and SR20DET (stock and aftermarket) side feed injectors are interchangable.