Throttle response

[f00g00]

Hi, Im kind of at a loss with the poor performance of my supra. My 0-60 times suck for my NA. It was in the mid 12's a couple of weeks ago. After checking all the inputs to my ECU I found an open winding in my distributer which I made an earlier post about timing. I fixed that and also found some broken wires on my ISC valve which I fixed. After fixing those two things I dropped almost 2 seconds to just under 11 seconds. Now my question is concerning the throttle response. I have a 5 speed. Im used to driving automatics both carb and injected. Both have very good response when the tranny kicks down at WOT. On my 5 speed, I don't notice much of a difference between 1/3 and WOT. My cable is adjusted properly and throttle body opens all the way but there just isn't much there between 1/3 and WOT. I did a 0-60 run only using 1/3 throttle and it was mid 14's. I took my K&N filter out and did a WOT 0-60 run and dropped another 1/2 second off, (it was recently cleaned and recharged) so that run was around 10.2. I recently changed the plugs to the nippendenso 2 prong ones
(I'm pretty sure that dropped the time a little) and checked compression and all the cylinders were 185 and 2 were around 190.
Im considering putting on headers in about 3 months after my vacation and a titan metal head gasket with ARP bolts. Am I wasting my money or should that help my performance?
Edit: just installed a set of denso iridium plugs and have a smoother idle but no better 0-60 time.
Thanx all