It's hard for me to think that cam walk can cause 2 to 3 degrees of change in the timing. What David was talking about (crank trigger) takes away all the movment of the cam and gives you the true timing. The cam twist and flexes due to driving the oil pump, it's takes 25 HP and more to drive an oil pump at high RPMS, especially if you're running heavy weight oil and pushing 60 to 100 LBS of oil pressure and that's where most of your timing change is comming from. That's why a crank trigger gets it right. Think about it the cam is about .800 dia. slightly more than 3/4" dia and 2 ft. long. That's why most of the big dogs run dry sumps and crank triggers and all NASCAR teams do.
I'm not saying your cam is not moving, but i am saying that a button will not correct the timing problem completely.
JMO
Zip.