for cheezy... Ratio i'm not sure...
but i'm using 4G13 engine with Mivec 4G92 gearbox, i may be less pick up, but it is for smooth compare to the stock gear box, 2nd-4th gear is much more power, higher rev. , higher speed...
if your budget not that high (sorry not to be mean), try 1.5 flywheel first... then change the clutch plate, not neccesary to put 1.5 or 1.6 , just get a clutch plate that provide u more smooth gear change...
if you are in high budget, i suggest you try this mivec gear box, i got one more with me in the moment, not hard to get from performance shop (not halfcut shop), cause usually people who really modify mivec and wanna have real performance they'll change their gear box to LSD type, so the they'll sell the mivec gear box...
and about the topspeed, try check your drive shaft and flywheel, they may be loose of threats or too oily... if there is no problem with those 2, check your valve, make sure there is no carbon stain on it...
most important, service your car punctually, use better engine oil and filter...
"You'll feel the differents" ;)