2jzgte aristo wont rev/miss at 5500rpm pls help

hello all

have a problem with my aristo v300 2jzgte auto ,its totally standard ..it starts perfectly runs smooth up until 5500/6000 rpm where it seems to miss or hessitate and if you keep your foot down it will struggle but will then rev right round to 7/8k

it seems to just hit a wall or like the rev limiter for a few seconds

i put in new plugs ngk r and gapped them to 0.7 but still the same

it will do it no matter if driving or sitting still in park or neutral no matter if you floor it quick or try to gently press gas pedal

ALSO when it hits this 5500rpm problem the engine light comes on then goes off

things im thinking of could be ,,coil pack leads? fuel pump? blocked catalitic converter? yes still has them on lol i wanted to get it running perfect before i start to modify it bit by bit ,

i tried to get the codes from the diagnostic port by joining the tc and e1 or whatever the two was to connect as my diagnostic port doesnt have connection in the tc1 as its a vvti but this just made nearly all the lights on the dash start flashing like an xmas tree ,,i did read if youve an immobiliser it can **** up diagnostic??? an i do have immobiliser

anyone else came up against this or any knowlage on it will be greatly appreciated

The ECU cuts power if it sees an error , different RPM,s for different issues , often this is not shown on the diagnostic codes :

1 the neural switch does this in an auto , but From memory it's lower revs - circa 3000

2 crank sensor also does this but higher up the rpm again from memory - (the crank sensor ring can also come loose)

3 Cam sensor again causes this

Check sensor cables , screens , and connectors too

4 MAF sensor also causes odd misfires , easy enough th clean first

5 the trac control can throw a wobbly too and shut the throttle plate open /close

6 water temp sensor again cause a misfire

7 the ignition module another source

8 timing out causes this , so belt jump or the solenoid that ports oil to control the vvti - clean filter first

It can be a real mare to find these issues , and Sod's law says it's the last bit you check or change

Note : the aftermarket coil packs for the vvti are shit !!!!!

The misfire at certain revs only in neutral also points to an ECU detected fault rather than a plugs /fuel problem

thanks ,,lot to think about i tried diagnostic again today and even though lots of lights are on the engine light gave me code 89 and 24 ,,,am i right that 24 is air temp sensor ? would this cause whats happening ?

anyone know what code 89 is?