paul,
we do a fair number of chinese and indian restaurants and always use prochem power burst as a prespray in hydraforce sprayer followed by an acidic rinse,
the key is really getting down enough prespray and having a lengthy dwell time, ideally prespraying again before cleaning, nice hot water aswell, most if not all of this black top will come of if you just allow the prespray to do it its work!
These type of carpets are normally quite resillient but obviously good to do the usual checks.
In my experience chinese & indian restaurants will always try and beat you down on price, so start fairly high, but usually if you do a good job they will be a regular customer and recommend you to their friends, so prob worthwhile
regards
steve