You can put springs on standard shocks, but you can only go so far.
Have you thought of a de cat pipe? I picked up one, second hand, in stainless for £20 from another Probe friend of mine before he sold his car. Mine will still pass emmisions with it fitted too, just, as it has two pre cats in the downpipes.
Old bill can be funny about front tints and they can test them with their machines too.