whats wrong with having a project, just giving the panda more grunt|!!! so it really can go in the wild lol
Adding more power isn't necessarily the answer if you can't get it effectively on the ground. If you're really thinking of off-roading it then all a turbo engine is likely to do is spin the wheels in the mud while a 999cc engined 4x4 will leave you behind. You're probably, and incorrectly, thinking that having a 4x4 in the Panda it will behave the same as 4x4 rally cars. It won't, as it doesn't have viscous couplings or LSD's for a start. It's a low speed/ low geared 4x4 system designed to work effectively off road in true 4x4 style. It's NOT a 4x4 rally car system.
As others have said, put a powerful turbo engine through the Panda 4x4 system and you'll tear the transmission, driveshafts and rear axle apart. You'll also not be able to go much above 40mph with the 4x4 engaged as it's not designed to go above that speed. This is stated quite clearly in the handbook as above that speed you must disengage the 4x4 and use 2x4 only.
Therefore if you want a fast Panda you should get rid of your 4x4 and start with a far more suitable 2x4 Panda. If you want to up the power for going off road then buy a more powerful off roader designed to cope with the power in the first place. However, bear in mind that what makes the Panda 4x4 so impressive is not its power but the fact that it is light and can use its small amount of power far more effectively than larger more poweful off roaders. And if you really want a 4x4 rally slag, buy one designed as such like an Integrale, Quattro, Sierra Cosworth 4x4, WRX etc.
However, if you really are intent on building a 4x4 turbo charged rally slag Panda then take a look at this site:
http://www.nyssa.ltd.uk/Y10/
You could do the same with a Panda seeing as it shares similar floorpans and construction with the Y10. However this is besides the point as you'll need to cut most of the floor pan out to cut and shut it with a shortened Lancia Integrale floor pan and drivetrain. How much time you have and how deep your pockets are will dictate whether you can even start to think about a project like this...