Broken distributor cap center pin

[AlexHillTVR]

Got a genuine Lucas rotor arm come through in the post today which I paid through the nose for. Along with that came a black Lucas distributor cap and a set of original spec HT leads albeit 8mm instead of 7. Replaced the otter switch too whilst I was at it. Replaced all very thoroughly. Anyways... Fired her up and all of a sudden there was a very notable improvement in idle but the car almost stalled at startup and there was a lot of shuddering. Let it run for about a minute until it started backfiring massively and was dumping fuel out of the exhaust from the start!

Suspected my new ignition components immediately and first went to the distributor cap to find the centre pin had broken off revealing the spring! I'll be taking it back to ACT tomorrow but I didn't expect that to happen!

Anyone ever experienced this and am I on the right track? Are the rotor and cap matched or not compatible? Was weird to see my tachometer reading a rock solid 800 rpm instead of fluctuating!