if your aim is a flywheel figure the ideas you have will get you there. You probably wont see more than 225bhp at the flywheel with an s13 t25 as a guideline.I would say that if your interested in fitting larger injectors then its probably worth you fitting a t28 turbo instead. You shouldnt need to fit a cometic gasket,Genuine Nissan ones do the job and as long as the car is setup right they shouldnt blow. A cometic one is nice for piece of mind or if you want to lower the cr, I guess you can decide on that once you have ported the head.
