This is wrong, one coil fires the front two cylinders 1/2. The other coil fires the rear two cylinders 3/4. You need to clean your carbs. It sounds like the idle jet circuit is plugged on the two RH carbs. That is why it picks up rpm when you spray the fluid in the carbs.
You have what are called heavy duty seals. They will work fine. Used more in race engines. I always put a little oil on top of the guide before pushing the seals on. It helps them go on easier. Like was said earlier use a deep well socket that fits over the valve stem.
Before installing the new races put them in the freezer over night if you can. A few hours at least. Then just before install take a heat gun and warm up the neck. Then take your frozen races and install them. They will go in much easier. I use a bearing driver to do mine. You can sometimes use...
If your machine shop has chatter from just surfacing a head you need a new machine shop. I've also had several heads that needed new valve guides. Very few people have the tools to ream those to fit. Installing guides is easy but fitting them takes the right tools. There is just some stuff that...
How often do some of you check to make sure the head and block surface is flat? If I have a head that needs the valve seats ground I have the head surfaced at the same time. Doesn't cost much and takes that possibility out of the equation.
There is more to nitrous than just bolting on a kit and hitting the button. If done correctly a GL engine could live happily. I have race bikes (with Kawasaki engines) that have a few seasons of races on them with no issues. Lots more nitrous that I would ever put to any stock engine. But engine...