mis firing then cutting out

[chris212]

After around 20 minutes driving today and as soon as i put my foot down it mis fired, the rev counter needle bounced around and it cut out. I pulled the bonnet up and checked the dizzy cap( recently replaced rotor arm as it has developed a slight miss and i thought it may be that). After 5 mins it started up again ok. It dove ok if i took if easy, but repeated the initial symptoms if i gave it some. It seems ok while its warming up.
Its a 4.3 pre cat. Any help appreciated!

[chris212]

Bought an amp today off ebay (powerspark). Its got the 3 pins but comes with the conversion wire . Hope this is right! Will let u know how i get on.

[chris212]

Fitted new amp. Made a huge difference- even reduced shunting. I'm still getting a slight stutter when I really give it some! Don't know if it just needs a few miles to clear itself out? I want to check the coil next. Any tips on how to do that? Is it just a case of testing the primary and secondary on the coil. If so does anyone know what the readings should be? Thanks.