yeah, if an engine sucks in fine dirt, does more damage to the sleeve/piston as opposed to anything else...
Tearing it down completely and cleaning it will save any further damage.
The one thing I'd recommend is to send it (piston/sleeve) to rayaracing.com for a pinch. This will return good compression to the engine. Should last a long time after that.....
BTW, I've driving all manner of engines, V-Spec, RB C6BB, WS7 III, S7, GRP .21, on and on.... I find the money is well spent on the better engines. They seem to perform better than the lower-end engines, longer life even when you are driving it at 99% holding nothing back....