I had cat back on my 220 XR8 stroker and it worked well. However, you have the smaller 200kW cats and the short 4-1 tickford headers. I fitted the Herrod 4-1 headers, however I used Supercats welded direct to header flange. The difference was unbelievable. I doubted it, but the results are definitely there.
I would be careful though, if you aren't going for big mods etc maybe interference headers are a better bet.
For reference, I believe the Herrod 4-1 headers are made by DiFillipo Engineering with specific Herrod design changes, and are made from full stainless steel (hence the cost).
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.