HOW MUCH TOP END WILL I LOOSE

I HAVE A 09 GSXR 750 I AM ABOUT TO GO DOWN ONE TOOTH IN THE FRONT AND GO UP 5 IN THE BACK TO HELP ME GET IT UP EASIER AT HIGHER SPEEDS HOW MUCH ON THE TOP END WILL I LOOSE SOME SAY NOTHING REALLY NOTICABLE AND THEN SOME SAY 20 TO 30 MPH
                                  THANKS RIP  

for every 1 tooth in the front it is equivalent to almost 3 in the rear.  

For every 1 tooth in the front down you go you will raise your RPM by 1000 to maintain the same speed.  soooo

if stock gears you could be in 1st gear at 6000rpm and do 20mph
if you go -1 in front in 1st gear at 7000rmp you will go 20mph

that's about the easiest i can explain it. I would only suggest doing made -1 / +2 or +3.   Start with the front sprocket at -1, you wont have to change your chain and will get a feel for the difference and see if you like it.  
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would it really matter much if you go from 180ish topspeed to 160ish??  

if you need to go -1 +5 to wheelie a gixxer 750 then, well, you really shouldn't be trying to wheelie to be honest.

-1 should be all the cheating you could need on that bike.