first make sure you got the O-rings out of the fuel rail and the intake ports. Make sure the injectors you're putting back in, the old ones or the replacement ones, have O-rings on the top and bottom. Lube the O-rings on the injectors before you put them back in. Use brake assembly fluid, dielectric grease, silicone grease... Install them into the rail first. then line them all up with their ports and push them onto the intake.
how far did you take things apart when you removed the injectors?