If by "bigger" you mean "higher flow" then you will increase the risk of oil starvation, as the higher flow pump will push more oil to the top of the motor than the standard pump. This will empty the sump more quickly, unless you add other oil control mods.
Read SK's oil control thread Here
+1 for N1GTRs tips, re 25% throttle, I think he just means take it easy until its warmed up, ie just drive at normal traffic speed. Also;
- dont hit the rev limiter
- dont use oil that's too thick. IMO ?W-40 is as high as you need to go with a quality oil.
- providing the injectors and pump are in good condition they'll be fine for 250