As
https://www.trueachievements.com/Zach+Cooper+FBI.htm said - this game is dead for it's online and doing a ranked match with a buddy is VERY easy.
This would not have been found without the help of
Peter SlocombeNow here is how you get this achievement with ease:
Start the game and go into "Multiclash" - this is the name they gave the Multiplayer mode.
Select the mode of connection (XBox live is probably what you would be using) and have one person create a Backlot battle match and the other people join that match.
Now, for the track - select "Overdrive 1"
When the race starts, turn around and go the opposite direction until the track turns. Still facing the opposite direction of the track, you should see two ally ways - one with the wood/barrels/cones/etc and one that looks like a real ally way.
What you want to do is drive down one ally way and then drift into the one next to it. There are plenty of items in both ally ways to keep your string alive, and enough room to ensure you can safely drift into them. It is best if this is done one at a time to avoid accidental crashing/string stealing.
Also you can use your Nitro boost while going down the ally ways to earn
You will gain another nitro boost for every 20 string increment (20/40/60/etc.).
Another note - after you get your 200+ string done, your buddy can ram into you, steal your string and gain
Also, you DO NOT have to finish the race. After obtaining the 200x string, you can just let the time run out and you will earn the achievement. All of the multiplayer achievements in this game will pop after the end of the race.
If you have any questions about this solution, please feel free to PM me.