These older models really need gold valve or something similar , you can fit them yourself , and they have spec sheet so you can change settings , I have been working on 14 and15 kx 450 air forks lately and changed to gold valves on compression and the mid valve on these models , what a difference , a lot better , they even turn better , so if you got spare dollars go all the way , the piston on these older models don't flow much and need to be changed , im not sure if the 99 has bladder forks or not but the 250 01 has , I disconnect the bladder system to get rid of the pressure in side , it works better and doesn't deflect half as much on sharp bumps and logs , hope this helps.