Right, i took my ST170 off the road over winter and i am just getting it ready to go back on the road in april. I am currently building an engine for the car but in the mean while i want a bit more poke. spec as it stands it

Typhoon K&N
Dreamscience
Mongoose Cat back
Exhaust Cam vernier retarded 8 degrees
underdrive pulleys
stage 3 clutch
Aluminium lightened flywheel
Short shifter
Ported TB
Full suspension/bush/brake rebuild.

Im running out of options, i did consider Bike ITB's but its allot of hassle for a short term fix.

The car has to have an MOT and last time it barely scrapped throught the emmisions test so its got no hope this time, i have just got a new lambda to help this along but am considering a sports cat.
Miltek do a sports cat and flexi pipe combo that looks good for £500, ford want £975 for just the cat from them and thats with a £45 surcharge back on the original cat

Will a sports cat make much difference, i wanted to fit new cams but the manufacturers do not reccomend the VVT being active on aftermarket cams. Bit stuck really, i have run out of options that dont involve big money and its the big money thats going into the other engine
Will a sports cat make more noise, i dont want the exhaust note any louder really
Thoughts?