Tach - wired it to the ignition coil - wires taken through the wirewall.
Boost gauge - T'ed out from one of the manifold vacuum/boost lines. This line is taken through the firewall and given to the boost gauge and on-board Race Dynamics ECU MAP sensor (ensuring that both the ECU and the gauge sees the same level of boost).
I was using the same liquid filled Autometer boost gauge in my supercharged VW corrado back in the US. Pulled it out when I sold my VW. I miss that car a lot !!!
You can run boosted without ignition control ( or offsetting dizzy) on low boost setup (4-5 psi). In such setup you may have to run slightly richer to keep detonation/pinging at bay. To get better performance and reliability its better to have some form of ignition control on boost.
Im running OEM
maruti clutch which does a good job till 12-14 psi. Beyond that it may be a matter of time before it gives up. For a while I was running 14-16 psi and the clutch gave up (started slipping on high boost).
My Maruti 800 has done about 21000 kms after boosting it. It hasn't given me a single problem except for a leaking turbo oil line on day 2 of the build. Had to replace the "banjo" setup and copper washer to get a good tight seal. The temp levels are comparable to stock on highways. But if you are constantly boosting like uphill etc the engine bay feels hotter than usual and the turbo/ manifold smells real hot too. Having said that the temp gauge has always stayed in its limit.
The overall reliability and the heat related stability may also lend itself to the appropriate range of AFR and ignition timing that Im running. Changes in that does impact the whole state of tune and reliability big time.
Peter - I hope people do more DIYs and enjoy their work/fruit also learning as they do things/mods.