i was thinking the same thing, bcpr 6 es.
like everyone has said, get a nistune fitted and tuned or any other aftermarket tuneable ecu, but call your tuner and find out what they like to tune before you go buy one,
Err no,
Lag time being off should have more of an affect at high engine speeds, Where piston speeds are much higher and the engine will rotate through a greater number of degrees during a given time interval
all injectors have lag time, bigger injectors normally have a bigger lag time as their parts are heavier etc.
when a factory base map is created on say a power fc the lag time is set to suit the stock injectors ie 444cc for RB26.
i think the lag time for 444cc is 77
so when upgrading to say 600cc lag time 80 there is a formula to calculate the new lag time needed into the power fc.
mine with this setup is 73% .03 lag time.
if you dont calculate it right then even though your reading the correct afr the power will be low because the fuel isnt spraying at the precise time needed, for example if sprayed too early it will sit behind the valve and wont atomise correctly.
and if sprayed too late (too much lag time) the valve will be already open and the fuel wont have enough time to be fully injested into the cylinder and the valve might shut leaving fuel astray at the valve till next intake cycle,
^^^what he said
are you using an aftermarket gauge, if you are already check the boost line going to it, make sure its not kinked or crushed blocked etc etc
take it off at home, good clean with degreaser and a good flush with water, do this till the water comes out the other end clean.
then let dry overnight end in the air with rags over the holes. refit the next morning,
thats a good thing then, atleast now you know and can move onto the next stage, elimination process.
next easiest thing take it into a good tuner and put it on the dyno,