Well, I bit the bullet and went the 160 route. Chris Flanagan did the conversion for me whilst 'The Mad Woman' (TMW) and I were abroad, so she has no idea anything's different.
Roxy's spec is now the 160 engine, plus Piper filter, Kmaps and TT Mk7 exhaust.. plus Bilsteins and new brakes with redstuff front pads.
Was the conversion worth it? Well, for me there's little or no difference if all you want is a fun, quickish car that'll bring a smile to your face. I had that with the 135, especially after the Kmaps upgrade which is, without doubt, the best thing anyone can do to improve their F or TF.
However, I wanted something that could surprise the sh*t out of the tailgaters and 'look at my new Audi' drivers that I encounter every day. With the engine upgrade, I've got it. Top end acceleration is addictive - she pulls like a train from around 4 to past 7K - and on the overrun the bangs and pops from the exhaust are as antisocial as you could want. Absolutely brilliant.
Now I need to sort out the understeer, so looks like a Seat splitter is on the agenda. I'm pretty sure TMW won't notice that either!