Castrol Formula R 10W60 - Brilliant oil

I had a feeling that the oil I had put in the Commodore was a bit too thin. It had developed a noisy lifter or two and wasn't running all that smoothly. I changed it for a fully synthetic oil yesterday, and although it cost a lot more for the oil, I recon it's well worth the money. I used Nulon Engine Flush to get the old mineral stuff out and it now idles smoother, which I didn't expect. I think it's possible that one of the hydraulic tappets was blocked and not extending fully, causing the valve lift on one cylinder to decrease slightly. I have never seen this much improvement from a simple change/upgrade of oil. The engine even seems to be making more power. The thing that struck me was how loud the injectors were, then I realised that it was because the rest of the engine was so much quieter than before.
I'm now planning to send the spare heads away to be crack and pressure tested and reconditioned, and maybe some larger valves. Although the engine idles better, it's still not perfect, and I think the valves on the head that I did not remove may not be sealing properly. Of course, I will be purchasing a compression tester this week so I can test them myself, as it could also be a number of other things, and I won't bother doing the heads yet if the compression is okay. I want to get the manual conversion done before any engine work happens.
One possibility is a faulty connection where the earth wires to the throttle position sensor and engine temperature sensor join to go to a common earth point. I have heard that these wires are crimped together and not soldered, they corrode over the years and cause the engine to idle roughly. I need to remove a lot of tape to get to these connections and am not looking forward to it. It will probably happen tomorrow, if I have time after bodywork. (Removing badges, sanding and finishing bonnet paint repairs, cleaning interior, and finishing rust repair of boot.)
I got a front grille, and a new glovebox (mine was broken) from EBay last week. I haven't recieved them yet, but so far the process has been easy enough. We'll see how it goes. If I get the goods this week, I will be buying a lot more off EBay in the future, as it is quite fun and easy, especially when you don't have much time for regular shopping. I find it hard to get my regular groceries, let alone exotic car parts.