Holden Jackaroo

Wecome to the land of the Jack - There are many things you can try including injector cleans off vehicle but really there is only one solution and you have found it PULP.
I have the same vehicle 2000 model and it drove me mad too - PULP will give you better performance and possibly better L per 100K so that offsets the cost a little. 95 octane from BP should be O'K and in NSW that is only 5c dearer, I don't know where you are but I guess the differential would be similar.
Caltex is only 6c dearer
If a refill is 50L that is $3
If you improve L per 100K by 1 that is 3-4 litres less per fill at >$1 per L

It is true that the some GMH dealers know bugger all about Jacks - my main issue with mine was that they didn't seem to give a hoot about customer relations and fair dealing - what they did give a hoot about was dishonesty - that they were good at.

95 PULP should be enough to do the trick. If not, then an off car injector clean is needed.

Mine had an off car injector clean at 60000kms (or thereabouts) and a bottle of Nulon Injector Cleaner goes in every 5000kms now too. I now run ULP without pinging and it is upto 83000kms.

I found that they suffer as soon as the fuel filter gets blocked up a bit, i change mine every service. Ex bosses jack had the ping the dealer couldn't fix , took me ten minutes to sling in a new filter and the prob was solved straight away.

Just my experience.
ps - i normally run optimax but it has no dramas running on regular unleaded either. Also don't be shy of blowing out the cobwebs on a regular basis....