blitz turbo timer.

PROS: Acts as boost gauge. Also keeps peak boost: which you can reset at any time. Don't have to worry about running off boost for a short time before you switch off (if that's how you want to drive: I personally don't and norm run off boost before my destiniation). Looks cool when you get out of your car with the engine running, then it shuts itself off & locks the doors as you walk away.

CONS: People who tell you that you haven't turned your car off.

Fitted by car electrician. Don't really do electrics (bar stereos) so rather pay someone who knows what they are doing to fit it.

There are lots of different types & manufacturers who deal wit these. They all have slightly different specs, so pick one which you think will be most useful to you: 1/4 mile times, 0-60 capability, boost guage with peak hold, lap times.