Hello everyone!

So I drive a 99' MX-5 with a VVT swap. I reused the 1.6 ECU from the 99, the wiring harness from the 99. I had to use an aftermarket Fuel Pressure regulator so that the fuel rail can be used as a return style system like it is in my 99 chassis. So I came to this problem when the engine is warm and I give it some revs, the engine rps drops to 400-500 rpms. It rattles really hard and is nearly about to stall every time as you can see in this video:
So I took the spark plugs out and all four looked like this:
https://ibb.co/sw52BD2

So, its clearly running rich.

Also found that the FPR is acting up somehow:
I set the fuel pressure regulator to 4bars/60psi when the fuel pump is priming (shorted FP and GND on the diagnosis)

so yeah, I dont know what to do at this point, and I am relying on some ideas of Facebook Groups and Forums. Hopefully someone can help!

 

Does the '99 1.6 have the secondary idle valve on the intake manifold? I know all the 90-93 1.8 swaps have idle issues because the 1.8s delete this, but I'm not sure if they were still around in the NBs.

 

I only have one idle control valve and had only one with my previous 1.6. However, I don't think that the idle is the issue here, since it idles fine at 900rpms. It just doesnt like it when I give it some gas.