Although I only drive a 'low torque petrol car'
, would agree with the comments about getting your car dyno tested at a minimum of two rolling roads to get an idea of the true power and torque of your set up. I.e. take the average as most accurate.
When I had my car as standard it made 229 PS at Jabba. When custom remapped at Jabba and sporting just a simple cone air filter it later made 274 PS - even on a day when the ambient temp was around 21 deg C with 95 octane in the tank.
Since then I have modded further with a 3" down pipe & sports cat (ceramic coated) and a cat back all from Piper. I also got the Jabba induction kit with a heat shield.
Went to Awesome in Manchester the other day, and with the ambient at about 15 deg C and a tank of Tesco 99 octane she made 276 PS. So that's a gain of just 2 hp for all those mods apparently!
Of course adding all that kit is going to see more than 2 hp gains, what's clearly the case is that Jabba's RR is not an identical set up to Awesome's and they are operated by different people.
The chances are that one reads a little high and the other maybe a little too low. So what the actual PS is I will never know for sure. I will probably use the same RR when trying to determine the relative gains as the car is modded, and use as many different RR's and take the average when attempting to determine the absolute true value.
As for the quality of Jabba's workmanship - excellent! As for their RR - maybe reading a little on the high side I think!