So likely replace both. Is it better off to replace the magnaride shocks or delete the air suspension? Anyone have good luck with aftermarket replacements?
what I would do is
1. feel the shock bladders, they should be firm but not rock hard after sitting overnight or even days or weeks without the pump running
so check them in the morning before you start the vehicle
if you reach and/or look under there and they are visibly blown out or deflated then usually this means they need to be replaced.
2. if they are not blown out but also not still inflated after sitting as noted above then they "may" be worn enough to be leaking air (spay them with a mix of dish soap & water and check for bubbles. (also spray the pump and air line connectors to check for more leaks)
3. if they are rock hard and not deflated, then it's possible the pump relief valve is not working
4. "normally" operation should go like this.
turn key to run, pump opens the relief valve for a short 1-2 second period to release some air so the pump is not stressed upon initial turn-0n, pump should inflate the shocks to around 20-25psi (vehicle unloaded). pump should shut off with a very short release of air. then air should hold. upon vehicle shut off after a few seconds the relief valve opens and releases a little bit of air it can be hard to hear and it may not happen "every" time. you would basically hear a small "click" and a light exhale while listening near the pump.
this should happen each key cycle, but not 100% always.
if the pump seems to be working fine and shocks seem fine then you go drive around a while, then stop and keep the vehicle running, reach under and feel the bladders they should still be firm, sometimes if they have a slow leak they will deflate and the pump will not run again until the next cycle.
basically you should do a little more troubleshooting to determine the issue.
there could be other things going on, bad ride height sensor, etc, but that would be on the more rare side and you would likely have a service system message or one would pop up eventually. in some cases you may not be able to exceed a certain speed I think 85mph because the computer see's it as a safety issue.