What rpm range? Rods are more likely to fail from tensile loads rather than compressive loads, and that usually means higher rpms. Of course just because Demon ran 8k rpm all the time and the rods were fine, that wasn't under boosted conditions. I'd say respect the 7000 rpm range as a hard limit when boosting above 8psi.
If you stay in the stock range then I'd guess about 10-12 psi is no problem for a daily driver with your compression on those pistons. I've already ran 12 psi more than once. I accidentally ran 14.7psi for a short time and the engine didn't even hiccup....the tires did though.
I'm having issues with one of my banks setting a lean code this weekend, but that is only under cruise conditions. Under full throttle it seems very safe. Probably an O2 sensor issue for me since I'm using a really old O2 sensor in that bank. I have a new one waiting to go in, I'm just lazy.
With a good tune and cool intake temps you should be able to run 15psi for short duration runs, like ocassional romps in 3rd gear. If you were doing an actual race on a straightaway boosting 15psi in 4th gear then I'd be adding octane booster even on a streetable tune. Intake temps will still rise and of course combustion temps go up quickly.
Runs in 1st and 2nd will just be tire burning bliss on the street at anything over 8psi.
Make sure that if you are going to really race several laps at boost above 12psi that you go up incrementally and do runs just listening for anything that sounds funny like pinging. Pay attention to exhaust temps and intake temps if you have gauges. Make sure you do some runs with a wideband O2 sensor at lower pressure then medium, and finally high pressure and see just what the O2 values are. You don't want to find out that you exceeded the limits of your injectors or MAF or fuel pump accidentally; even if they are "supposed" to handle the boost you calculated, something may not be right.
Best to test 15psi on the dyno where you can watch the torque curve for signs of jagged torque indicating spark issues that can come from either fuel or spark plugs. But still, don't be afraid to try out a 15psi run if everything else looks fine leading up to it.
BTW, I'm running 8psi daily right now. Very strong. I have to feather the throttle in first gear and of course when I engage the clutch in second. But if the road is good and I engage the clutch smoothly then I can hold 2nd gear at 8psi.
If FordRule comes back on he'll probably give you a first hand story about the acceleration because he was around here on Thursday and I gave him a ride.
