First Golf Gti. Few little niggles to be sorted.

[Mav]

Got my first ever performance car the other month and after much research and debate I decided on the golf mk. 2 16v. Leather interior and revs like a V-tech, What a car.
There are some little problems though. Firstly the car is running slightly lean, is this due to the fact that I have a performance exaust and can this be ajusted manually or do I need to remap. I am also getting 270 miles out of a tank with conservative driving, so will this improve with the improved mixture.
Secondly the MFR is showing 20mpg most of the time and when i'm doing 70 its showing 6mph, the oil temp is also non existant. Could this be due to the fact that i I brought the car with 17"s on it and the computer needs recalibrating? And is there anywhere that I can get this sorted?
I'd appreciate some advice, Thanx.

[Joe12]

Just take it into a VW dealer and ask for a quote. The price will be sky high but you don't have to have it done there and you will at least know what is wrong with the car in detail.

[Gambit]

get it serviced by a VW specialist, (dont go to VAG!!!) then get it on the rollin road to get it setup correctly

my MFA always shows around the 19-21 mpg for in & around town

most ive ever got is 30mpg!!

as for the oil temp, there is a current thread on here that will tell you how to test it

any pics?

[Harooshum]

270 miles is what i normally get from both my 8v and 16v.  Another way to test the AVERAGE speed and AVERAGE fuel consumption is:

While on the motorway, hold to a steady speed like 70 for as long as poss, then reset it.  After a few seconds, it should show 70 or just under 70, which means it's working fine.

Also, try doing the same thing but keep an eye on fuel consumption, and after you reset it, should show quite a high figure especially if you are going downhill at 70 in fifth.  Or while going very fast, slip the car into neutral and reset the MFA.  When it comes back on, should show a consumption figure of around 99.9. lol.

Harry