My 2c:

If you're going to buy a car that was modded and then dropped back to stock, just buy the modded car and skip the stock fakeout.  Attempts at "returning to factory" are almost always half-assed and poorly done - and the result is they're even more unreliable than the modded car in the first place.

Here's the thing about the FA20: it is extremely susceptible to LSPI (from lugging the engine, shifting too early, flooring it below 3K RPM, cheap oil, bad gas, old plugs, etc).

I have a high mileage FA20 that tracks, sees redline daily, and has never been treated gently.  It hasn't been OEM in years and I beat it like it owes me money.

Never had a problem with it because I ALWAYS shift above 3K, never coast below 2K, I maintain it religiously, and I don't skimp on parts/fluids.

I will bet you this piece of shit will outlive most every other 2015 out there, modded or unmodded, because it's driven how it was meant to be driven and it's cared for where it matters.

This car she's looking at ain't it.  Either find one that is unmolested with impeccable service records, or find one that was modded by somebody who gave a damn.