Same with mine, but the car was a total dog above 4k it was pointless and below 4k there is no power to begin with, so I had to do something. Till I replaced the IMRC, I pinned the secondaries open... there were some side effects, but worth it for having at least most of the power above 4k.
I am not sure why you didn't have a CEL saying that it wasn't working right, I sure did... not that I needed one telling me that something wasn't right, but I sure had one.
