Thinking back over the years on this site, the mod I liked best was putting an electric motor in the air intake to boost the boost. It was the size of those motors you have in your PC running the cooling fan.
No dyno figures were shown but I reckon it would produce a microwatt or so extra.

Now there was a serious (pardon) mod investigated by our founder Jamie P.
I think the idea was to switch the intake / exhaust manifold directions, quite logical -to reduce pipe length for a FMIC. I do not recall if it actually succeeded.