Ok mates has a silver top rb20det in a r31 s2 silo.
If you flaten it it comes onto boost it bogs down until 3500rpm then takes off then hits a wall again at 4800rpm we have tryed new plugs gaped at .8mm, cleaned air flow meter (also tryed a diffrant air flow meter) new fuel filter and r33 fuel pump but still no diffrant. also if you free rev it it limters at 6200rpm but dosnt sound like the proper limiter
Anyone have any ideas what to look at next
All thats done to it is cooler, full 3inch exhaust and 12psi (some times 14psi)