Once you are level 3 or higher you can unlock the reverse engineering in the research facility, once this is done you can spy on peoples cars and clone parts. To actually spy on them you select the team and part you want to spy on in the drop down menu in 'Design'
I think you can actually spy on them from level 1, but before you get reverse enginering you can only see their level (of the components). You can not do anything with it. Don't kow if you can reverse engineer thing at level 3 you spied on at level 1...
Procedure is in design, choose a team, choose a part you want info on, and wait till after a race (no sneaking into their research facilities, you have to look at them during race day). .
Got to level 3, got the research facility, got the reverse enginering skill..... You can actually reverse engineer stuff you spied on the first 2 levels, before you had the reverse enginering skill.
I had 3 parts that were 16% on my car, about 80% on my opponents car, and I got about 16% increase in performance on them, by reverse enginering. Not cheap (at just short of a milion a try), but a quick way to catch up