latest conspiracy theory: I think I'm only getting 1/2 of the RPM signal due to how I wired my GM coils. I decided to be clever & wire for sequential spark. I followed the instructions in the VVT megathread, but I added two signal wires which go directly from the ECU aux connector to two of the coils. Would this screw up the tach sig?
*edit*
No that doesn't make sense. The ECU is sending out the tach signal. It should be independent of the coils. Why would I only get 1/2 RPM???

Your MS3 should be calculating the RPM's from the cam and crank sensor. Then sending it out to the gauge cluster over the tach wire. No clue why it would only show half the rpms.

were you able to just drop the vvt head on to your BP05 block? I though the vvt head needed a vvt block? Maybe your crank position sensor is misplaced a little bit?

​​​​​​​VVT head will drop onto any 1.8 miata block with zero issues.

Can you screen shot Tach Output and ignition settings? I'm not allowed to install Tuner Studio on work computers.

Can you verify in Spark output mode that the order in which the coils are wired is correct? When I was switching from batch fuel and wasted spark to sequential, it wasn't trivial.

The oil pump needed a little modification to accommodate the crank sensor. The crank sensor appears to be sending a signal. I'm not savvy enough to tell whether the ECU is getting the signal it wants. Consensus was that I will likely need to adjust timing with trigger wizard like ya do on a cas car. It may be that I need to check timing while cranking to get into the ballpark.

Wheel decoder settings are good? Is this a stock trigger wheel?

You are using the OEM 4tooth trigger wheel correct?

Yep. OE 4 tooth.

I thought it need the special high volume oil pump? or are all 1.8 pumps considered high volume in relation to 1.6 pumps?

I was already running sequential injection before I swapped in the VVT head, but yes, I'll need to run through the spark & fuel test modes to make sure nothing is wrong.

Yes you should use the high volume oil pump. That does not stop the head from dropping onto the block. I am using a 94 block, BE VVT oil pump, and a VVT head to make my engine.

Can oe trigger wheels be mounted backwards? I never had one.

Interesting the cam input label is different. Yours says CMP, which makes sense. Mines simply called MS3X cam in.

It looks like it can be put in backwards: https://forum.miata.net/vb/showthread.php?t=575508

I'm hopeful I can check without pulling the timing belt. I think I can feel for that pressed in TDC marker to see whether it's convex towards the motor

IIRC, the junkyard​ crank pulley & timing wheel I bought had obvious scum indicating which side of the timing wheel had spent a decade up against the crank sprocket. But I will definitely check into it.

Here's my plan of attack tonight:
trickle charge the battery
Validate spark sequence in test mode (can I use the timing light?)
Validate injectors are still working correctly
Validate timing wheel isnt backwards
Check timing while cranking

Any other ideas? I know, these are basics I shoulda done already.

In output test mode, just grab an old spare spark plug and stick it in the boot end. Enable the spark test, and see if it sparks. Has to be grounded on something, I just left it on top of a heat shield and it sparked away.
Is it reliable to check timing while cranking? Isn't that only done once the motor kicks over?

wackbards, did you use a high volume oil pump? I might be doing the same things if you got away without it.