What is the benefit or downside to using thicker gauge wire to upgrade or repair the current ecu wiring harness. Im going to start rebuilding mine soon im wondering.id prefer a gauge step up unless it will cause problems with resistance. Although I wouldnt think so.

There is almost never a problem with installing a bigger wire. There is no equipment in a 914 that is sensitive enough to require a smaller wire and the lengths are to short to matter. Most manufactuers install the smallest wire that will handle the RMS (70% of max) current load. I would suggest changing every single wire in a 914 to the next size bigger wire. Larger wire will reduce resistance and help your electrical system preform better. This has the biggest effect on headlights. They will be much brighter with larger wire.

Mark -

Talk to Jeff Bowlsby - he rebuilds the engine harnesses for 914s & can guide you best. You may even decide it's worthwhile to just get a full set of engine bay harnesses from him, but he'd probably be happy to answer the question by email or PM even if you're not buying from him (but I think he's out of town through next week).