Engine sputtering at about 65

The wiring of the plug wires is a mess. Have you checked for correct firing order?

Unfortunately all of the wiring in this car is a mess. Also unfortunately I bought it this was so I have zero idea what corners were cut and how jacked up it fully is. I'm guessing that I wouldn't get it running half way decently if the firing order were out but I'll have a look and make sure.