VP 3.8 slight surge/hunt on throttle

[VPCalais38]

My VP V6 has started hunting slightly.
When the car is cold there is no problem.
It's fine at idle and anywhere over 1/4 throttle. But cruising at almost any speed when warm it has a slight 100-200rpm surge and if I slowly depress the throttle there is no real acceleration until I get to 1/4 throttle then the car acelerates hard.

The engine has a C.O.M.E cam and chip, JP Racing timing chain and gears, extractors and a polished TB. But it has never had this problem before.

I have done the following:

New CAS (Old one failed)
New NGK Plugs and leads
New Battery (not related to issue)
I have swapped coil packs around with some spares I have
I pulled a TPS off another TB I have and tried it
I cleaned the TB
Checked manifold and vacuum hoses for leaks

Pressure tested the fuel system. The manual says when I clamp the fuel pressure return line after the regulator the pressure should jump to 380KPA and if it goes higher than this the reg should be replaced.... mine jumps up to 580KPA so I fitted another set of injectors, rail and reg to mine, but the problem hasnt gone away. All other tests were fine for the pressure tests.

I checked fault codes and get a 12 which indicates no sensor faults logged.

I changed the MAP sensor with a spare one I have.

Only thing I haven't tried is DFI module (I have a spare).

Anything else that could be causing the problem?

Am I safe in disconnecting the O2 sensor and driving the car? Was thinking of disconnecting it when the car is at running temp and seeing if it goes back to cold setting and fixes the problem.

[COTTER]

Try cleaning the stepper motor, that might help.

[Rusty]

Transmission??? Just guessing....

[joe seinfeld]

Transmission??? Just guessing....

i drove mine around with the o2 sensor unplugged for a fair while, especially when i bought it, drove it home which was a 50 min trip becuase i didnt know it was unplugged, just makes the car a little rougher.

dont know if it does any real damage, im sure it would after a while though

[joe seinfeld]

didnt mean to include the quote there

[Fu Manchu]

Clean the IAC in the throttle body.

[vn calais lookalike]

often when u pull apart the throttle body u need to reset the IAC done by pressing it in before fitting it onto TB this usualy works for me 8)

[Tuff-VP-Wagzz]

have you upgrading your air inductions?, alot more response with an induction