I replaced my Terrafirma +2" shocks with the Britpart foam cell shocks and prefer the Britparts.
The foam cell shocks have almost no resistance on compression but lots on extension so they absorb bumps on the road really well whilst still providing enough damping to stop the 'bouncy castle' feeling. Also, they are not gas pressurised so are much easier to fit and remove (unlike the Terrafirma shocks that won't budge until every bit of your blood is in your face and tears have started to flow)
Also, with the +2' shocks I tore an Arnott airbag out of the crimp ring which then deflated with a bang. The shocks limit axle travel and prevent the airbag from being stretched so don't use extended ones unless your suspension has been lifted. They may be OK with OEM bags as they are not crimped and can pull apart slightly, let out some air, and re-seat again.
