I'm getting 23.5 at WOT according to the ECU. Is 28-28.5 what the ECU is supposed to think, or do I add the 4-5 degrees of additional advance, in which case it looks about right now?
If you are reading the data from the ECU it will read 23.5. When you take it to the dyno have somebody stand outside with a timing light as you do a pull. You should see 28 or 28.5 total timing rock solid. If it is there is nothing wrong with the timing. However, while you are on the dyno make sure the butterflies snap open at roughly 5500. They should open and not float around. I have had the check valve go bad more than once and will certainly cause low TQ.