running lean and dont know y

[boosted240sxnut]

hey yall my 1990 s13 ka24e is running lean it runs very good cold but when it starts warming up it hesitates very bad i replaced the o2 sensor the maf sensor air temp sensor fuel reg. and new ecu i searched and cant find eny thing but the timing. but i took a timing lite to it and it was in the right spot i can rev above 3500 rpm but getting there it stumbles if i push the gass very slowly to the floor it will rev high but i cant stomp it or push the throttle hard please help me its pisin me off i want to finnish my sr build