240sx SR20 problems

[TougeChallenger]

Just wondering why this stuff if happening. when the turbo begins to spool up after around 3500 rpms, it starts to lag a little. it also has a rough idle when it is cold sometimes, and after alot of hard shifting the clutch begins to slip after 4000 rpms. ill just be cruising along and then bam. the clutch will start to slipo. ive already put a new walbro 255 pump, a nismo slave cylinder and a nice clutch set in there and there problems are persisting. although after i did the fuel pump the problems got alot less frequent. it just sucks because when i am in the middle of a decently long corner, my rpms will start to drop and ill lose speed. any suggestions as to why these things may be happening?any information would be greatly appreciated.

[9240sx]

Fuel filter,Spark plugs?