Here is a side qustion that has been iching me..Did Mazda put the 0-60 restrtiction there to keep us or try to keep us from snapping rods, cause the knew they f'd up with the tooth pics we have??
I think MSMS3 is on the mark with his post. It's more for vehicle control at wide open throttle.
I've worked in the aftermarket performance/racing industry for 15 years, 5 of those years for a company that manufactured connecting rods, and I've never seen a rod break due to low RPM torque. Most connecting rod failures I have seen where the the rod was actually the cause of the failure was from stress. Heat and fatigue from high RPM's are usually are the cause of these types of failures. Engines with extreme cylinder pressures, such as turbocharged, supercharged, and nitrous assisted engines can add more stress to a connecting rod in high RPM conditions, but typically low RPM torque levels don't cause those types of failures.
The load on the rod increases as RPM increases. Stresses from increased cylinder pressure from increased boost levels at higher RPMs can cause stress failures, but the biggest rod killers on these cars is going to be detonation. Detonation can almost double combustion pressures. Incorrect ignition timing, lean air/fuel ratios, and increased boost pressures at high load and high RPM's are the main causes of detonation (the dreaded knock!) on these engines.
The Mazda ECU has a very sophisticated knock control system built in to keep detonation from tearing up your engine. That is why having the mass air calculations correct is such a big deal, and why we don't remove the factory protecton systems with the Hypertech tune.
Running a large air intake without the MAF reading corrected will make a bit more power, but the resulting increase in boost, and leaner WOT air/fuel ratios make it more succeptable to knock (detonation), and engine failure.
And as Darth said, the load on the engine is greater in the higher gears, at the lower RPMs. That is when the engine is most succeptable to detonation. The torque spike itself isn't what will kill the rods, it's the stress caused by detonation from excessive boost and lean air/fuel ratios (and bad tuning) that accompany the torque spike. That is why we keep the boost levels in check, and make sure the tune maintains the proper air/fuel ratios to reduce the risk of evil(evil) detonation.
Chris