In comparison to my AE86 GT-S...
 

When I hit the gas in my new FR-S, i feel like it takes ages before the RPM's move.

Individual throttle bodies and cable-operated throttle linkage are always going to feel faster than a single throttle body and throttle-by-wire. If you have a lightweight flywheel in your AE86, that will also make response faster.

It may be the electronics. A friend in his car something was wrong with the gas.

A tune will great increase throttle response. For this reason alone I've been considering the Ecutek flash.

How much does that ECU flash cost?

Not sure about the Ecutek, but the Visconti stage 1 is $750. Apparently worth every penny from what i've read.

I'd say its mostly the ETC. I think an ae86 with a 20v has a better power to weight ratio as well but don't quote me on that.

The power:weight ratio is roughly the same, but it wouldn't have a bearing on throttle response anyway.

yikes.. just found this thread by accident.
I have been trying to find about this info but i guess wrong keyword..

I got AE86 and was at one time using quad throttle and Integra with carbs and Altezza.. I really wish the throttle response in Altezza like my other cars and one thing that that hesitate me with GT86 is about this. So is the lag in throttle response in GT86 is it better or about the same with Altezza?

you trolls are trolling, the 86's throttle response is amazing, i've had to ease up on my usage of the throttle since i got it.

He's not talking about throttle sensitivity. He's talking about the amount of time for the car to react after hitting the throttle...

Would there be any way to go from throttle by wire to mechanical linkage or would this be too expensive, backwards and stupid?

Not stupid... but too damn expensive