At the beginning of last week, I noticed that my turbo gauge is going up a hell of a lot quicker than usual - I haven't done anything different except filling up with Tesco's high octane petrol
Is this a good thing or a bad thing???

filling up with tesco petrol..... id say a bad thing havent a clue about your turbo gague tho. hope you get it sorted easy enough.

A few of the fellas on the ATR website reckon that Tesco 99 RON is normal petrol thats just bulked out with bio-ethanol Doesn't mean a great deal to me, but apparently isn't a good thing

fuel wont really have anything to do with your boost rising. Is it still at the same boost just spooling faster? or is it going up past were it normally use to sit?

very true but bio ethanol isnt good for turbo engines .

turbo gauge in an mr2 is pants full stop. ive just fitted a splitfire boost gauge to my mr2 , and its accurate

Well not quite It can stop your boost going up as quick if you have shitty fuel..

Paul.

it just goes up very quickly, eg in 4th at 60mph the gauge is all the way up - it din't normally

If I were you i'd get a boost proper boost guage mate. easy to fit and much more accurate than the stock toyota one.

Paul.

mine goes off the scale when i hit boost ! i wouldnt worry about it . this is the reason i fitted a boost gauge so i know whats happening .

as above best getting a proper boost guage buddy and see what it reads at and then fined out what stock boost pressure it should be running

if I let mine go off the scale, my engine management light kicks in and it dies pretty much, for a little while afgter I can drive but if i put my foot down again, rather than getting boost I just loose power and engine light comes back on

That'l be fuel cut then!

Paul.

as paul said sounds like FC you will need to get that looked in to , seems like you have either boost spike or just over boosting.

could it be due to a leak/loose pipe going either in or out of the turbo? had a look and the pipe (think its coming from the air filter) doesn't seem to be on 100% Maybe it thinks its getting more air than it is

The pipe that goes to the air filer, or just after it, is usually the recirc pipe from the BOV......that wouldnt make you overboost. It would make you run rich if it was not connected though.

Cheers,

Paul.