Don't know if it's any help, but my XR3i turbo is running a Newman cam too and I'm pretty chuffed with it!
The spec:

Standard bottom-end with new pistons, shells, etc with ARP bolts
Standard head (bar the Newman cam)
Stage 2 T3 on standard manifold peaking @20psi, dropping to 16psi
Magnex 2.5" bore exhaust
GRS intercooler
VEMS management



Christian and Gary went through 3 different specs of Piper cam (best RR result was 180bhp) before giving up on them and slapped in the Newman one- something to do with high exhaust temps?

They said it could go further with more tweaks, but I ain't got no money!