Don't know where you're getting your information from, but you're wrong.

The stoich is different. Call VP, and they will tell you. As per my experience with MS109, fueling changes are indeed required.

Retune the car for the fuel used, and never assume anything.

 

There are 2 "versions" of ms109... regular ms109 and ms109e.. 109e is oxygenated and will require a fueling change. Regular ms109 should not

This is the description of ms109


MotorSport 109™
In engines that can run on pump gas, MS109 is a direct replacement that produces more power than any other unleaded fuel - up to 5% more than premium unleaded. Recommended for applications with up to 25 lbs of boost and naturally aspirated engines with CRs up to 15:1. Compared to other unleaded fuels, MS109 offers better detonation protection as well.

MS109e
MotorSport 109E™
MS109E is designed for the same applications as Motorsport 109, offering the same substantial power increases and protection against detonation. Oxygenated with ethanol, MS109E can be used in all 50 states, including those that restrict the use of MTBE in fuels.

Also, I use ms109 quite a bit and it usually doesnt take much more than a small tweak or 2. no major changes have ever been required for ms109 on any of the cars we've run it in.

 

"In engines that can run on pump gas" doesn't mean the stoich is 14.7. Again, I've spoken directly to VP and my local VP distributor on the matter. As well as experience using the fuel.

Fueling changes are required.

 

it says MS109 IS A DIRECT REPLACEMENT, and this has been my experience. On the cars we use it in no real changes have ever been required. On cars that are just too high compression for pump gas we have been able to pull fuel out and pick up power. I'm not saying re-tuning for the fuel wont make more power, i'm saying if you are at 13:1 afr on pump gas and dump in ms109 you'll still be at 13:1.

 

DIRECT REPLACEMENT is a broad term buddy. Like I said, call VP. The stoich IS DIFFERENT.

MS109 is 13.41:1. Period. Unless the laws of chemistry and physics cease to exist under your engine bays, then I don't know what to tell you.

Maybe you're running your ECU with closed loop o2 feedback and haven't seen a change in lambda.

However, every motor I've tried it on requires changes to the fuel map.