[supremeefi]

Yes on the TFI distributor the #1 tab on the reluctor wheel is offset, that's how the EEC-IV knows where #1 is. And yes if you have an ECU that can read that then you can go sequential. But I believe the MassFlo system comes with a standard Mallory distributor. I'm pretty sure it fires in batch, not sequential.

But don't lose sight of the fact that while sequential is good, changeable/programmable sequential is better, sometimes much better. Watch the O2 correction as you change injector timing. It will change noticeably no question.

Watch my video on the Accel DFI website. The Mustang I refer to had a 246/249 @ .050 hyd roller in a 427W. They sent the ECU back 3 times, got 4 or 5 different chips, they lost count. Ran like ****. Chris at MassFlo tried to help but nothing worked.
Put the Accel Thruster on it. I put a base tune in it and it fired right up and idled fine. Runs great, guy drives it almost every day.

Also have a buddy who put 226/230 @ .050 cam in his 5.O, didn't run well either. When you said they have their limitations that may be an understatement.