I wouldn't just attack your TPI with a file and call it good. You'll probably mess something up. Porting and polishing, when done right, is done with highly abrasive carbide bits and an air powered inline grinder. Or at least around here it is. I would take it to a shop, they will probably port and polish your whole setup for less that $200. Also, as an alternative you could look into some of the options offered by TPI Specialties. Their Big mouth manifold produces great hp and torque. Either way, you'll gain some ponys.
67-327, 700r4 trans, 9:1 Comp XE268 Cam, Perf. RPM Intake. 750 Holley, Sportsman II Heads, Ceramic coated headers