I discovered a good way to fix wire insulation
 

perhaps you needed to splice into a wire ( without cutting the wire) or used a quick splice and now want to remove and fix the insulation. found a product called 5 second fix. basically it is a epoxy that cures when exposed to UV light. It looked interesting so I bought it at a local hardware store and used in on a scrap piece of wire. it is not perfect, but much better compared to tape and it takes only a few seconds. thought it might be of interest. several similar products exist and I've not tried them all but to me it seems like a great way to patch up those hacked wire harnesses. solder or crimp the wire and use this as fill. many people say solder is bad it can corrode or fray the wire over time which is fair but properly sealing the connection also seems like part of the argument and this product does a pretty good job and is likely way better compared to tape. shrink wrap is good but difficult to use in tight spaces and small gauge. this is not the fix all that the ads suggest but for some applications I think it is pretty cool. not sure about how it does in a hot engine bay but worth spending 5 bucks to test, at least vs electrical tape. it is not as strong or durable as they suggest so do your own testing