Originally Posted by Captain Cotswold

Looks like you are rocking the original engine harness, with the 3 large connectors across the bulkhead.....



From factory, the way they are secured means they're kinda bent back on themselves and stressed. Any change in that area by previous owners means they likely have some serious tiewrap strangulation going on too which makes it even worse. They can give running issues if they've any moisture in them, or are disturbed so give them a good coat of looking at if the coil wiring doesn't end up being at fault.

Just a personal thing but I noticed you don't have a heat shield over your turbo, or under it, or over the turbo side engine mount. If it's running 340ish and you've been enjoying it, your turbo's gonna have been whacking out some serious heat to everything in that area. Certainly your bulkhead brake pipes and all the switchery around your master cylinder.
Hope some of this helps. Just my opinion based on what you've described.