Help find Lego number for large Technic F1 Ferrari
This is set 8386 Ferrari F1 Racer 1:10.



It's hard to tell from your photo exactly what is missing. Obviously the rear spoiler is missing, but there may be several other smaller elements missing.

Brickset and LEGO.com both have the full instructions, so the best way to determine what is missing is probably to walk through those. Here they are:

https://www.lego.com/biassets/bi/4280172.pdf

You can find the complete parts list for this set on Bricklink if you'd like to order any replacement parts.