I have a wierd issue, the car will rev up with or without load fine, but when cruising at a steady speed, the engine starts surging. Like it's running out of fuel

If the pedal isn't released it will cut in and out, although if the pedal is released for a sec, and then pressed again, the car will gain speed again fine.

What could it be?

I think I have this exact same problem. For me it happens at any speed (as long as it's constant) in any gear, however it is much more pronounced at lower speeds. In a car park you'd be forgiven to think I couldn't drive a manual to save my life (it'd look like I'm dropping the clutch and bunny hopping everywhere), but I can still kind of feel it through the accelerator pedal even at 100 in fifth (well, I think I can anyway). Then, if I release and reapply the go pedal, everything is fine again.

I've looked all over these forums and the internet in general for a solution, but I can't even find a similar problem, let alone one with an answer. I'm not quite sure if it is the same issue or the same symptoms, but from what you're saying it sure does sound like it. I'll get it on video if that helps.

it could be the throttle position sensor, its the only thing i can think of that would cause this

Changed and adjusted TPS, no luck.. Anyone else have any ideas?

Unplug the oxy sensor and see if it does it still

How about your fuel filter? If it is getting blocked, or if the intake to the pump is partially blocked, it could cause a drop in delivery pressure and then starvation. The ECU will then compensate and probably over compensate, making it rich. Another cause could ba an air leak in the intake system, leaning it all out too much, then the ECU catching up and overdoing it.