Ok, I've seen people use this for the boost pipe leaks but not seen any links or sizes, anyone done this who is willing to share?

My plan is replace/upgrade top pipes and heat shrink the bottoms ones.

Anyone?

I can measure if you want, guessing 60mm wouldn't be far off.

Size of pipes?

There's a lot of heat shrink stuff out there. Some of the better stuff has a heat operated  glue set inside the ends of the heatshrink, and it makes a seal on the pipe as it shrinks,ad the glue sets.

But, I'd ask if heatshrink has any place under the bonnet, as once used & set , it prefers stable thermal conditions. If damaged ,it splits easily- one method used to remove it- make a small cut in the sleeve and heat- it  curls back fron the cut.