If you a seriously thinking of running 20 psi and an additional 100 shot on top of that with stock ignition, the only thing I can recommend is to do some more research.
Granted, I'm not an expert, by any means. I just don't want to see you pre-detonate this thing. From my experience, the stock coil over plug ignition is pretty good. But when you start throwing in 2 power adders, (one of them being pretty extreme), I would definitely look into upgrading. If you've got that much money in the motor, another thousand or so on a solid ignition is not going to break the bank..... Better safe than sorry.
There is no way the stock bottom end will take 20psi much less that and 100hp shot. Please don't kill your pony, there are many write ups on making huge power out of the 4.6 mill.