TTI. Shorties

Auto or stick car? The TTI have larger primaries then Schumacher but the Schumacher are longer in design. No significant performance difference in the two. I’ve had both. I noticed in your avatar pic you have aluminum heads, do they have raised ports? This could also be a limiting factor.
Ian

The alum head are stock height ports , but do have angle spark plugs. IDK if that would be a factor with the TTIs.