Trust me the extra thickness of the Topgun is going to do SFA on a N/A and on a moderately tuned turbo. the only time the difference will be noticed is when the leads are totally buggered, or are reaaly really old.. or your running high power/boost.
when i bought my leads (non genuine from twosrus) there werent any genuine toyota ones available for a cheap price
now twosrus stock them along with genuine cap and rotor and the price is very very good for what your getting compared to buying locally.
the tune up kit made a big difference to my car and fixed my misfiring under high load/boost.
so in my case im not sure wethere the cap, rotor or leads were faulty but i did a general maintenance and changed them all at once and the improvement was quite noticable. so noticable that i started hitting fuel cut lol
btw the aftermarket leads i have and others i have seen dont fit well in the lead holder thats on the engine bay. cause they are thicker and dont press into the holders properly. not a big deal but just thought id mention yet.
cheers