My '79 308 has a 'lazy' Tach/leading to sequence of repairs, upgrades, maintenance ?s

Just going through and sorting my car the last couple weeks, I will post a more comprehensive update on my car's thread (http://www.ferrarichat.com/forum/showthread.php?t=258265) soon, but I have an issue I want to run by you guys before I get too far ahead of myself.

The tach on my '79 308 has been 'lazy' since the day I got it. I searched a bunch of past threads and saw that 'jumpy' tachs seem to be a common issue, but found nothing regarding my particular issue. Basically upon applying throttle the tach is very slow to react. I would say that the lag between the engine increasing revs and the tach following suit is about 1.5-2 seconds. At idle it seems to be reading correctly. It is hard to tell if it is reading correct over idle though with the long lag times and the revs coming back down.

Like I said this issue has been persistent since I got the car and the car has been through several different states of running conditions since my ownership; misfiring on several cylinders, back to running on all eight, to running rich.

The reason I am posing this question at this point is because I have a Pertronix setup for the dual dizzies that has not yet been installed. I have been holding off on this installation due to the fact that me, and my buddy who have been working on the car, have no idea how to wire this setup. I am not sure if I should go ahead and tackle the Pertronix setup as it may alleviate the tach issue altogether, or maybe even perhaps cause some new tach issues?

Once the running rich issues has been sorted the car will be in a good driving state. I plan to rev the crap out of the car so this tach issue is something that needs to be rectified.

Forgot to add, not this is not complicated enough already, but I have also been holding off on the Pertronix install because at 28000 miles my car is coming due for a valve adjustment. Not sure if the best course of action at this point is to go ahead install the Petronix, adjust valves, adjust the timing, then worry about the tach or go ahead try to solve tach issue now, get the fuel mixture correct, drive the car for another couple grand (which could take a while) then tackle the Pertronix, valves, and timing? I just changed the timing belt btw.