I have a 2001 accord sedan with the standard trans. Put a “40,000 mile” motor in it with a jdm F23A head. At first it was in limp mode because of a vtec malfunction but now I’ve fixed it (cooling fan switch and vtec oil pressure switch connectors were swapped). But now the car only revs to 5,000 to 5,500 rpm. I know there’s nothing electronically wrong with it. But I don’t think the valves have ever been adjusted. However, in my experience with Honda if the valves are too tight it won’t have compression for as long throughout the stroke and cause it to run horrible. Or if they’re too loose they makes noise. In my case, they don’t make any noise and compression is good. If you hook a leak down tester up it read good. Any insight?

 

If it's hitting a limiter and you have no codes or CEL, then it's operating as intended and your tachometer reading is off. It's a fairly common issue usually related to the ICM.