How much PSI goes into the suspension on my 1990 ZX10 and is it compressed air or nitrogen.

PSA (Pressure Swing Adsorption) and VPSA (Vacuum Swing Adsorption) are both methods used to produce nitrogen from air. The main difference between the two is the pressure at which the process takes place.
In a PSA system, air is compressed and then passed through a vessel filled with a specialized adsorbent material. This material selectively adsorbs the oxygen, leaving the nitrogen to be collected. This process takes place at high pressures (around 100 psi).
In a VPSA system, air is first passed through a vacuum pump, which reduces the pressure inside the vessel. The air is then passed through a bed of adsorbent material, which again selectively adsorbs the oxygen, leaving the nitrogen to be collected. This process takes place at much lower pressures (around 25 psi)
VPSA system is typically smaller and less expensive than PSA system, however, PSA system is capable of producing a higher purity nitrogen.

better than car tires
truck tires are inflated to 100 psi and because of the weight they carry , they generate more heat so the nitrogen is the way to go
unfortunately , tires get punctures well away from any nitrogen pump so it is not cost effective

The trouble with Tire Pressure Sensors (TPS) is that they are in my opinion, too sensitive. Even a drop in tire pressure of 2 PSI seems to set them off. You may notice that the light comes on in the morning (when it's cool) but goes off after a short drive. Once your tires have warmed up (either from an outside temperature increase or by road friction) the air in the tire expands, increasing the tire pressure slightly, -usually satisfying the TPS and the light goes out.

I've used both of these methods to solve this issue: Get your tires filled with nitrogen (less expansion/contraction than air) or you could increase the tire pressure at the air filling station by few PSI.

These are Spheres, and should be changed with knowledge about the hydromatic system.

Pressures of 500 to 2,700 psi in the system. Spheres are pressurized to 2,700 psi new with nitrogen gas. Expected life, 6 years.

Call ALBERS of Zionsville for parts and information.

first you have to have a EPA certification too purchase, and to handle Refrigerant. in order to stop the leak first it must be located and in most cases soldered shut depending on the leaks location if the leak is in the tube sheet of the coils it my be better to replace the leaking coil. if the leak can be repaired the refrigerant must be removed from the system, leaving it in a vacuum then bring it up to atmospheric pressure (0 psi) using dry nitrogen. then the leak can be repaired, after leak has been repaired pressure test system at 120 psi for 20 min. watching gauges to see if pressure drops. If pressure holds, release nitrogen then evacuate system with vacuum pump. most manufactures require a 500 micron of less vacuum to ensure no moisture is in system then charge system according Manufactures Specification. charging and service ports are normally located at outdoor condensing unit where copper piping connects too condenser, charging manifolds are a necessary tool for this repair. I would highly recommend having a HVAC contractor preform this repair, amount of refrigerant that goes into the system is critical to performance of heat pump operation.

The volume is less than about 1/2 quart - it's usually not measured going in since you fill the shock completely - there's no need to measure. Some guys assemble the entire shock, then fill with oil and cycle the shaft, then install the bladder cap last. My method is to install the shaft and seal head and the bladder, then put about 2 PSI in the bladder, then bleed through the compression cap. My method is a bit more complicated to explain, but it's effective at eliminating ALL the air from the oil and it keeps the bladder from being installed in a collapsed state.

As far as the nitrogen charge - 145PSI is stock. 130-160PSI is typical.

In general, most of the KYB and Showa big bike suspensions are charged to around 140-150 PSI from the factory.

you cant air anything up it is nitrogen filled the only thing you can do is buy a stiffer spring from someone like race tech suspension and you could also have them revalve it to your weight. or you can do it yourself.