Was having the same problems myself with boost, your best bet is to check all your vaccum pipes, there's probably a split or cracked pipe somewhere. Theres also the vaccum solenoid underneath the plastic engine cover, your throttle cable is bolted to it, mine had packed in which was part of my problem, have someone check that out for you too.
As for the whole re-map business, if you intend on keeping the car standard i wouldn't worry about a re-map, just run your car on Maxol E5 and booster (which you can get from the traders on here) and you'll be grand. Service your car regularly and don't thrash it and you won't have to worry about melting a piston. If however you are gonna start modifying your car ie de-cat downpipe, front mount intercooler etc then a re-map is essential to make the most of your mods. The re-map will help reduce what we legacy drivers call the valley of death but it won't get rid of it altogether.