Have you tried a 5d distributer instead of the 4a? A little engineering and I can still boost and I think it is a little lighter too...if I remember correctly???
I did that
Went for the Engine mod and got +39.80% eng capacity and +10% recharge rate and a loss in cap and rec rate for all others of approx 10%.
+40% on a 5D is just enough to allow you to boost