Todays candidate for "best thing I bought for the car" is a micron oil filter from Moss. It's a direct replacement for the standard GFE150 part but has part number GFE24 instead (and is twice the cost)
I had one of these fitted to the race engine last season due to the normal part being out of stock at the time and today I've just visited the engine builder who has pulled the engine apart after a seasons racing. The oil is very clean, almost new looking and the big end bearings are hardly worn. I know I don't do many actual miles in this car but those I do are on the circuit and the engine gets thrashed. Triumph 1500cc engines aren't supposed to rev regularly to over 6000rpm (getting on for 7000 on occasion) and I'm very impressed with the complete lack of gritty stuff in the sump. Chris the engine builder remarked on it too.
So I've just ordered two more of these for this season (one for running in and another for running after that). They seem to "do exactly what it says on the tin" and keep the crud in the filter and not circulating round the engine.
On a related note, when I originally drained the oil before removing the engine from the car, there was the remains of a broken split pin attached to the magnetic sump plug. It turns out that it came from the front of the rocker shaft and must have broken off and dropped out at some point. There's a bit of the casting broken from the rear rocker pedestal too so it looks like the rocker assembly has had a hard time. Both problems are easily fixed though fortunately.
The van came back from the local garage today with a nice shiny new exhaust fitted. In the end it proved too difficult to make up the necessary custom pipe so the garage have removed the internals from the old damaged catalytic converter and just put the empty casing back in place to join up the system. Seems to work well and it might be just my imagination but it felt more lively on the way back from the garage as though the old exhaust was perhaps partially blocked. That's not too unlikely in fact as the cat was damaged and the rest of the system was rusty and full of soot from the old engine burning huge amounts of oil before I took it off the road.
It's hard to properly see any improvement on the 1 mile drive from the garage in traffic though! If I can sort out this gearbox fluid leak I'll give it a proper test sometime.
I had a fun time last weekend touring the Dales and sorting out some more of the route for the CT "Dales Bramble" along with Caroline and Paul. I think we have a more-or-less complete route now and it should be a good event later in the year. This weekend's job is still planned to be fitting the new race engine in the car, assuming it's back together in time. Currently it's expected to be finished on Friday in time for me to collect it.