If you would like to get a better system for your 90's there are quite a few great options out there. Now, seeing as how I am a Fromeco rep you can guess what I'm going to recommend but I firmly believe in Fromeco's product quality as well as their customer service. They WILL take care of you should the need ever arise.
Fromeco offers two different levels on their battery packs for heli's, one being the Relion's and the second, and top of the line being the Peerless packs. The Peerless uses fantastic cells of the highest quality but make no mistake, the Relions are also of very, very high quality. Personaly, I use the Relions but the choice is up to you. Note: If you don't have one already you will need a charger capable of charging lithium cells(Lion/Lipo). If your not sure about your charge tell us what one you have and we should be able to advise.
This link will give you alot of info on cell types etc, this is your best bet for great information: http://www.fromeco.org/shop/apeerlessadvantage.htm
Here's a little more info on cells: http://www.fromeco.org/shop/aufmythbusters.htm
Here is a link to Fromeco's "Knowledge base" which should have some good reading if you would like to learn a little more about their systems and basic questions customers have had or may have: http://www.fromeco.org/instantkb/
The Arizona regulator is a fantastic regulator that is basicaly two regulators in one. It will send a straight 5V to your gyro and this is not adjustable. But, you are able to adjust the voltage going to your receiver to anywhere from 5V to 6V thus allowing you to adjust what voltage you want your servos to run at. More voltage, more torque and speed. I believe the Arizona is the standard by which all regulators should be judged by, it is just solid, reliable, consistant. A true work horse. And here is a link to it so you can read up on it: http://www.fromeco.org/shop/aarizona%20reg.htm
So, for your 90 this is what I, and many others would recommend:
4800 mah battery pack, Relion or Peerless, entirely up to you.
I do and would recommend that you get the Deans/16ga wire upgrade on both the pack and the Arizona. It's only $4.50 and worth every penny.
The 4800 mah pack will allow you to fly all day without worry but do, as you would/should with any batteries, check them often with a load checker. Your "No FLy" voltage is 7.0 with a 1 amp load. It would be your choice of whether you wanted the Relions or the Peerless, again, both are just fantastic packs. Here's the link of where to buy em:
And here is the link for the Arizona regulator:
I know I'm a bit long winded here, sorry about that, but I truely believe that Fromeco offers the best product out there for the best price. You will be very happy with this setup and if you have any questions please feel free to pm me. Hope I've been of some help, good luck!!
Fromeco Field Rep.
A day without sunshine is, well.., alot like night time.