steering rack help reqd

[biffbangpow]

just bought a 16v redtop, the steerings a bit notchy in the center postion the racks not leeking or anything.
any way of fixing without replacing the rack
how many types of rack and are they interchangeable, i,e from a 8v or v6 etc
or must the be replace with the exact type, ie matching numbers on rack

[biffbangpow]

anymore info reqd ???