That step change you are referring to is a key point of modification by Tickford on the 220 engines. Makes a huge difference in flow to match port the intake. You can do it yourself if you know how to set up the gasket for drawing the outlines.
I had someone else do it for me when they did the heads!
BA'1.5' Pursuit 290
Lightning Strike / Reflective Orange Stripes
'General' Dog - AP's German Shepherd and Best Mate - 02Dec1998-15Dec2003.
'Pepper' Dog - General's and My Little German Shepherd Sweetie - 1996?-02Apr2006.
'Sako' Dog - My Beautiful and Pretty German Shepherd - 2001?-23Aug2006.