[cny]

It could be a full transplant. Its pretty common out in the 02-05 Civic Si. Does the vtec come on strong at like 6k rpms (a distinct different motor sound) If so then its probably a K20a2 out of an RSX-s. As for the front fenders meaning there was an accident....thats probably not the case, many people change the stock fenders out for those.....but in my opinion they are very ugly and tacky looking.

Heres a couple pics of my old 03 Si (ep3)