S5 Non-Turbo RX-7 misfires under load

Hi everyone! I’m in the process of getting my car tuned by Tuned By Shawn and am dealing with an issue with ignition. This has been a problem before my first tuning appointment with him, and my next appointment is in more than a week so I was hoping to knock this issue out and take the car out to get more data. So basically what’s happening is that the car idles fairly smooth at 1000 rpm, and when under no load(clutch-in) runs smooth even up to redline. However, under load, the car pops and bangs like crazy. This also occurs when I suddenly stamp the throttle. Basically whenever manifold pressure “increases” from vacuum towards atmospheric. I want to say it’s misfiring as compression numbers haven’t deviated much from when I acquired the car. All this to say I don’t think it’s knocking. My setup is below.

Year: 1991

Make: Mazda

Model: RX-7 (Series 5 FC3S); Non-turbo

ECU: Haltech Nexus R3

IGN-1A Smart Coils(Direct Fire)

Electric radiator fan

Electric water pump

ID-1050X injectors (primary and secondary)

Walbro 255 fuel pump

Radium FPR set to base pressure of ~43.5psi

Stock CAS trigger system

OMP delete(premix only)

Air pump delete

Swapped to turbo 2 lower intake manifold

Secondary port sleeves have been removed

FD upper intake manifold

Emissions system/rats nest delete

Thermowax delete(retain IAC for cold start & idle control)

Engine has been street ported

I have locked timing and confirmed with a timing light that it’s set correctly and I have no DTCs claiming timing issues. Thank you all for your time and consideration!

Has the ECU be setup / tuned at all, or are you just using a base map without completing the setup.

When you confirmed timing, did you increase the revs and make sure it stays fixed at higher engine speeds?

ECU has been configured, and has been slightly tuned by TBS. Tuned to the point where it should be drivable at least(he said to drive around and report back with how it performed). I admit I have not checked timing at higher revs, however, this issue doesn’t occur at higher revs when unloaded. That is something I will check next though, thank you!