Early 308 GT4/GTB/GTS cars with a double S159 distributor ignition setup are difficult to maintain as wear and age changes the advance curve of each distributor individually, e.g. both banks run with a slightly different advance which reduces a bit of power and smoothness of the engine. To fix this i did an installation of a Pertronix MR-183 setup with two pickups in one distributor (the second distributor just distributes the spark in such a setup), as a result the advance curve for both banks is controlled by just one advance curve. The engine ran a lot better but still not as smoothly as expected, so i benchmarked the S159 Pertronix setup on a distributor tester and found out that the difference in advance between the cylinders was up to 4-5º. Bought another unit but had similar results, apparently the position of the magnets in the sleeve is not precise enough to yield better results. After that i decided to adapt the Bosch high performance ignition setup i did for the Dino 246 some years ago, this setup uses a Lumenition Optronics OS50 optical pickup and a Bosch 0227100137 high power ignition module combined with the matching Bosch 0221122334 coil. For the S159 setup, a full setup is required for each bank and both Lumenition pickups are installed in one distributor (i opted for the front one). The Lumenition #262 chopper wheel required for the optical pickup fits nicely on the S159 cam after a bit of sanding. The first Lumenition pickup has been installed in the position for the front bank (0º), the second one for the rear bank is installed at 135º (a multiple of 45º) starting from the first pickup, so with the #262 four cylinder chopper wheel each pickup serves one bank. Testing the converted S159 distributor on the distributor tester yielded a cylinder difference of less than 1º The engine ran very smooth after the installation and hot and cold starts were much easier compared with the old points setup. I also installed a fresh set of NGK BPR8EIX for best results. This setup has a similar approach and precision as the very effective Marelli AEI200/Magnetic pickup setup in late GT4/GTB/GTS cars, but delivers 33% more power due to the higher coil current (and 100% more power compared to the factory points setup). It's a bit of work machining the adapter plate and wiring up the parts but it's quite worth the time from my experience. Also it looks quite original. See below for pictures and the wiring diagram of the new ignition setup.