CYLINDER COMPRESSION READINGS

I have done a compression test on my 4.6 gems today as i am trying to track down a slightly wavering idle, every cylinder is within a couple of lbs psi of each other but do they seem right or are they a little on the high side.(The block and heads have obviously been skimmed) Your thoughts would be appreciated.
The engine is a 4.6 that has been rebuilt twice (they messed up the first time and had to do it again), It was done 3 years ago now, and it has a piper 270/2 fast road cam fitted and top hat liners.
Compression is 193 to 195psi accross the all cylinders.
I posted before christmas about there being a low vacuum and this pointed to the ignition timing being out due to the camshaft, so my other question is do you think a tornado chip would help as it seems the gems engine management will not let the timing adjust to where its needed.
My lpg has given up and i am going to have a new system but i have to get it right on petrol first so any inpuy would be appreciated.
Thanks all
Mark