Originally Posted by
Doingitsideways
Reading the op back...
You mention piston cooling.
On a B20F?
New one on me, as I thought they didn't have any cooling, one of the reasons you can't turbo the 2 litre.
Does sound like a collapsed cat, especially as it picks up at high revs.
Probably worth doing a stage 0 on it though. Especially the fuel filter and ignition side of things - spark plugs, HTs, dizzy cap, rotor arm, coil. Just ignition problems tend to be exaggerated at lower revs.
Saying all that though, I've found my 160k B20F to be MUCH quicker and free revving than my 55k one.
The high mileage one has a bit of piston slap from cold, but once warm it keeps with a standard turbo easily.