Here is an excerpt from the new york times

"The transformation is similar to that of carbon. Under high pressure and intense heat, graphite, the most stable form of pure carbon, changes into diamond and remains diamond even when the heat and pressure are taken away."

Ron/ Stacey; I just have a quick question here:

If the part "and remains diamond even when" were to read, "and remains thus even when", will this be correct? or is ""and remains in this way although" better?

"remains thus" would possibly be fine. it sounds a bit stilted and archaic, but i've certainly seen that kind of construction before.
however, it's also quite possible that the gmat will deride that sort of construction as wordy / awkward / unclear (especially "unclear"; the gmat requires a very high standard of precision in SC sentences).
so, the jury is out until we see evidence one way or the other on an official problem.

--

"in this way" would NOT be fine, because no "way" has been described. in fact, no adverb is present at all to be properly parallel to "in this way" (an adverbial construction); diamond is most certainly not a "way" of doing anything.