Here's what I've done to my 4 cylinder '99 Accord (F23A1 engine):AEM cold air intakeDC Sports 4-2-1 headersApex World Sport catback exhaustUnorthodox Racing Super Street pulleys (no longer under the super street model)Neuspeed Front Upper Tie-BarNeuspeed short shifterApex World Sport Coilovers (lowered car)18" Konig Tantrums wheelsMy Dad also has a 4 cylinder '01 Accord (F23A4) and when I do drive his car while visiting, I can tell a huge difference in performance and handling. The pulleys were the last modification and it seemed that's where the best improvement came from. The car responds a lot better on take-off and on acceleration. My car has been a blast to drive and still outperforms some of the newer and bigger V6s out on the road.Both vehicles are 5 speed manual transmissions.
My car: http://uploader.ws/uploa