1999 Honda Prelude Start up issues

Hey, I been having some start up issues recently. Sometimes, when I attempt to start my car, it turns over for about 6-8 seconds before starting and its sometimes a rough start. I've changed/checked everything I could possibly think of. I've changed plugs, wires, distributor cap, rotor, the whole distributor, a new starter, battery; I've changed the throttle position sensor, MAP sensor, Fuel filter; I've checked the fuel pressure at start up and its around 45 psi. I've put in every possible chemical to help clean things internally but I've always kept up my maintenance schedule. After a hard start up, and I run it for a bit, turn it off then attempt to start it again, it starts right up. I believe one other possibility could be the crank position sensor, but that about 10 mins away from takin the timing belt off and I've been trying to avoid that. Does anyone else know what else it could be or believe the same theory about the crank sensor? If it is the crank sensor I'll gladly change it but I would like some reassurance before. At least I can change the water pump out while I'm at it, haha. Thanks for help, if any!