[olddog]

Cam change likely increased the dynamic compression ratio. Do you know what the static compression is?

Get a wide band O2 sensor on it. Make sure you are not running too lean. At WOT the AFR should be around 12.5:1. You can go as rich as 10:1 to help with the pinging, but you would likely loose some power.

As you are already trying, retarding the timing will help. I would not be doing too much with the timing until I had the fuel correct. Typically with fuel injection people pull about 5 deg out of the timing until they get the fuel dialed in, just to stay on the safe side. They don't work on the timing until the fuel is right.

That would be my strategy here. Pull timing until is stops pining. Then make sure the fuel is correct. If you are already at 12.5:1 at WOT and your timing was pinging at say 30 deg at 3500 rpm, you can try going to 10:1. If it pings at 10:1 30 deg at 3500 rpm then you have too much compression. You would have to lower the dynamic compression with the cam or lower the static compression.