Courtenay Sport for Superchargers. Vectra B 2.2 16v Supercharger Conversion Stage 2 - 240 bhp and 220 lb ft torque £5175 fitted (requires Sports Exhaust System).
Stage 1 Conversion - 210 bhp £4750 fitted and Turbo kits are available from Regal at around £3500.
There are a few options other than the above, it just depends on how far you want to go. I had the Courtenay CS4 package which consisted of Modified head, pre-cat removal, 200 CPI sport cat, airbox mods + K&N filter, cool stat and remap. I also had to have my inlet guides replaced and that came to £2200. I then went back 8 months later for more head work and a set of Schrick cams which gave me the Courtenay CS5 package. That trip cost me another £1750.
Other members like Zafman and Vocky have also got tubular exhaust manifolds.
It all comes down to how big your wallets is.
8)