I own a 1991 EX Civic with a JDM DOHC ZC . Recently I bought an AEM fuel rail because I wanted a guage and adjustable fuel regulator for tuning . I am installing reground cams and adjustable sprockets later. I thought that the extra gas would not matter much now , as I could adjust the fuel pressure to prevent a rich condition. However I had to reduce the fuel pressure all the way to 31psi(controlled) to get it to run right. A week ago I put the stock fuel rail back on and it runs great. It runs so good I am afraid to mess with it. I left the psi at 31. Do ZC's like to run lean? I have no ping and the plugs look good. Should I bring my psi back up to 35,or is it ok to leave it at 31? The only problem I noticed is on cold days below 40 degrees the car sputters and stalls when I first start it. It starts flawlessly on the second attempt, and runs great. Sometimes I will turn the key, let it crank twice, turn it off and restart, it then starts and idles down fine.