4G13 to 8k is normal for me, that why when go 4G91 cab can only go 6500 ~ 7000 rpm...everytime reach it will kick back or drop then go to 6700 will do again and agian....
My 4G91 cab got 1 ECU with 2 big socket (1 for cab / 1 for ing timing)
nothing block the carb....event the 2nd barrel...