Just spoke to the Service Advisor on your enquiries.
1) It will take about 2 weeks for the parts to arrive for your installation. Reason being they need your vin number to order the powerkit
2) after installation the powerkit should increase your torque by another 40Nm and horsepower between 16-20hp
3) cannot comment on the fuel consumption as it depends a lot on how much and how frequently you stomp your car. Anyway, If you drive as you would normally, you'll probably lose only about 50km for every full tank, that is instead of 900km you might get only 850km
4) the powerkit will not void the car warranty nor affect your insurance since it is supplied and installed by BMW. But if you install from outside (unauthorized dealer) then the warranty will be voided.
The Service Advisor said the current price of below 8-grand is a promotional price and he's not see how long it will last. Was informed that the price is all inclusive including all peripheral parts and labour which could possibly come to 4-grand as the installation of the powerkit will require, amongst others, an upgrade of the intercooler, electric fan, some circuit board, re-programming of ECU (or so I was told). Apparently when promotion ends like those for the e90 the powerkit retails at above RM11,000.
Hope the above helps.
Cheers