evening

i have just had a new bottom end put in and ever since i am getting a strange drop in the revs when sat still idleing???

so i have just purchased a genuine maf and about to change my lambda sensor but cant find out what lambda sensor i need as my one is a bosch and ends in 97230 and a friend of mine which had the exact same car ends in 02070

the car is a uk year 2000 impreza

if anyone can help that would be great!!