Hi I recently just changed my coolant outlet pipe on my 2004 ls v8, had to get my battery charged & when i started my car today and reved up to about 2000rpms i got a signal sayin ETC engine failure.....the car didnt shut down but i lost power...i drove around the block it was driving fine once i was under 2000rpms, any suggestion as to what the problem is, i dont really live in the states so taking it to a dealer is out of the question...