Fuel filter and fuel pressure regulator is in the tank and isnt serviceable. Sometimes the pressure reg in the tank fails and takes time to start as the fuel line loses residual pressure overnight. That said we need the fault code first matey. or we just guessing
thats isnt a nissan fault code im afraid. You need to look with the leaflet you may have with the scanner. K12 has no shut off valve. It has a start signal thats all. If it wont rev above 2k its possibly gone into limp mode. You need to establish a fault code. EOBD all have the same codes, for example something like a misfire would read po300 for multi cyl misfire p0301 cyl 1 misfire, p0340 Cam pos sensor etc etc. Some cheap ones off ebay give the eobd codes. Go to your local Nissan dealer ask one of the techs to plug consult in, proffer a tenner it usually helps, then come back and i`ll tell you how you can fix it.