If your top speed is limited by engine power (as opposed to hitting the rev limiter) then a turbo will increase your top speed.
It'll also reduce the time taken to get there.
...i couldn't get over 65mph-70 steady no matter wind and grade.
True, but he said that it didn't matter with wind or other factors. The turbo WILL help greatly on power and torque. If it's hill climbing power the turbo will help, if it's pushing through the wind the turbo will help but simple top end speed, the turbo will NOT help.