No power after 2000 rpm

[Callump]

Hey guys, recently got my mini out of storage for the winter, over the winter I got some head work done, larger 35mm intake valves, de shrouded and mildly gas flowed head, with 200lbs springs. I had a Nikki twin choke downdraught carb on there which gave me no power after around 2000 rpm, although before I had the head work done it would accelerate nicely all the way through the Rev range. I’ve recently put a HS4 on with a BCE needle which from what I’ve seen seemed quite suited to my engine and I have a hi lift cam, lcb manifold and decat straight through exhaust. But with this needle the car won’t even start, I’ve also got an AAB needle, which also gives me no power above 2000rpm. The car also makes a very different noise when I’m getting no power. Any advice on why I’m getting no power greatly appreciated, cheers.