Recently got my 2008 Volvo C30 R-Design 1.6 petrol second hand. Was driving it a low speeds for a while and Everything seemed perfect. However once I took it on to the motor way the car shudders between 60-75 mph, especially when accelerating...I went and got the front tyres replaced, rebalanced and realigned, but to no avail the shuddering continues!
Any insight in to what this could be would be great thank you.

Have you had any luck fixing this issue? Having the same exact issue in our 2008 Volvo C30 T5.

what happens with the shudder if you ease off the gas or even drop the car into neutral at speed? Anything change if you apply the brakes? Did you also balance the rear wheels (what happens if you rotate the tires front to rear?). Given this happens at speed I'd start with things that rotate - axles/boots in good shape? brake rotors/hubs? engine motor mounts? are the accessories like power steering pump and AC compressor secure? Finally, is there anything loose which the wind can be catching? ie engine shrouds, valances etc?

Engine shudder under load is the fuel pressure sensor

For my 2010 C30 that was shaking, shuttering upon acceleration at higher speed. Replacing the right drive axel fixed the problem and smooth since.