The key to a smoother running engine is having the injectors balanced, preferably at 25 PSI +/-. If you have all 5 well balanced, then having them set at 1,900 PSI for example in a turbo engine with worn nozzles that don't pee, then you should be OK. However, the spec's are the spec's. The FSM is 50+/- PSI so you should be good if you balance them at 1,900 since you are still within nominal spec. A BAR is 14.5038 PSI, so 135 x14.5038 = 1,958.013 or a nominal 1,950.