Well while driving home tonight Code po335 popped up.
-P0335 Crankshaft Position Sensor Circuit

I have tried clearing the code but it just comes right back on after a short amount of miles. The car doesn't want to start up, takes a second or two to finally kick over. Once on makes a little clicking noise but don't know if that has anything to do with this code but runs fairly good. The car is in desperate need of a tune due to new exhaust manifold, 02 housing, intake, and test pipe.

So after reading around the only conclusions ive got is the battery, sensor, dirty bad connections, or timing belt rubbing sensor..

Where should i start?

Any help would be great!
Thanks
Scott