I'm guessing that you bought these second hand and were "told" they were Ahmed springs, when in fact they were just some cheap aftermarket ones, as the Ahmed springs are a LOT stiffer than normal springs.

Can you tell me where you bought them from and what numbers were stamped on the "pigtails"?

Andy,
I missed this earlier .

Seriously, the 6° rear end transforms the handling. In fact I would have suggested that this is more important than the fitting of coilovers (the handling would have been transformed with this and just some good quality dampers and springs). I did a big write up on suspension for Fast Ford explaining why - perhaps you have this somewhere and can have a read?

Be careful about buying the base Adrenaline version, as this is not adjustable for toe and has caught a few out who have expected it to be. The £1k Ahmed one is adjustable for both toe and camber.