not 100% sure, 3 bar is usually only fitted to stage 3 cars.

If you have a 3 bar map sensor and a chip expects a 2 bar one, the chip will not interpret the map sensor readings properly and won't fuel the car as it should (amongst other things). It will either think the car is under more (or less - that's where I am not sure) than it actually is.

If you are not 100% sure what you are doing, give Mark Shead @ MADevelopments a call and see if you can book her in for him to have a look. He's in maindenhead so not far from slough.

He will most certainly sort your problem out, and it probably will cost you less in the long run.

His mobile number is: 07768 356204