My car was running like crap. Took it to a tuner, threw it on a dyno, attached a fuel pressure gauge, found it was running lean.
Was told to change the pump. Did that, and did the filter too. Helped but was still running sluggish esp. near redline. Needed my timing adjusted and serviced my AFM. Squeezed like an extra 10rwkw just from that and gave me much smoother power curve.
That's my story