VG33 Light Power Loss Mid-Range RPM's

[hakanerdogan]

Hi there,

1997 Nissan Pathfinder SE Auto transmission VG33E 138.000 miles

I have mid range power loss but it's very light, especially when the engine is under load. It's like a giant animal sits and stands up on the truck very high frequency.

At the higher revs and below 2000 it runs like champ.

Truck starts perfect
Idles like metronom
Transmission is perfect.
No SES light.

What I did

-brand new Hitachi distributor (very expensive)
-new NGK plugs
-new Yazaki plug cables
-new drivetrain fluids (all of them according to manuel)
-new MAF (hitachi)
-new timing and alternator belt timing set correct, this is sure
-new water pump and thermostat
-new exhaust (whole) no leaks
-not suspicious about the injectors or fuel pump because it makes the same power loss both in LPG and petrol
-oil, oil filter and air filter new

I don't know what to do after that moment. I might think its due to clogged cat but so why it's moving like a monster at higher revs? Also vacuum leaks is suspicious cuz its running fine when you flat it.

Any ideas welcome, Thanks.