I have a 1990 formula with a 305 tbi that I am in the process of converting to tpi. I was wondering if putting on self aligning 1.6 ratio roller rockers will make a noticable difference or should I stick with the factory ones. (yes I know TBI heads are not as good as TPI heads, but that is what I have for now)

Here are the changes I have so far.

Tpi unit, plenum ported.
LT1 Cam
GM LT4 springs, retainers, keys

 

You should definitely get some real rockers, as opposed to the factory rubber ones. Just going from flexible ones with ratios all over the place to ones that transmit the full lobe profile with consisstency from valve to valve, makes all th difference in the world.

There will be essentially no difference whatsoever between 1.5s and 1.6s as long as you keep the other, tighter restriction of those anti-performance TBI heads on there. Even with good heads, there will be little difference. I'd recommend sticking with 1.52s, since if you go up in the ratio, you'd be at risk of pulling out those pull-out rocker studs. Get the Comp 1417-16.