Im running stable 308 fps and rate 30000, but when playing ffa and there is alot of action going on, ping isnt stable. Is there anyway around this?

Go to another server? the xs4all / other ffa servers lags depening on how many players are on it playing..

So no... no way around it.

Isn't this the case in any (Quake) game?

Increasing rate would help if the server allows this.

However seeing that you are already at 30000 makes me wonder if the pingtime is somewhat near frametime (in this case averaging aroung 0,5ms below 12,98ms or 25,97ms and so on). In this situation increased packet size would cause increased latency regardless of the rate setting and that would make your ping unstable.

If possible, try using through local qizmo and server side qizmo (you need to connect through them both) and try ezcomp3 if it helps.

Check your netgraph.
If you are getting any yellow lines, this means that your rate is insufficient.
Or you could use the more modern "show net" (aka r_netstats 1 from mqwcl) which should list any 'rate cut' packets.

On a heavily populated server (say 12+) with large open areas it is quite feasible that 'peak' downstream data could exceed 30000. A few years ago I did some testing and found that in most cases 25000 is sufficient however it does depend a bit on the map; i.e. smaller maps with plenty of easily accessible particle weapons are more likely to cause trouble. Something like "Powder Keg" is likely to need a high sv_maxrate setting.