Alright guys so essentially long story short, im on the verge of buying a 2011 RR sport Supercharged, it only has 57k miles clean title clean carfax etc on it.. but heres the catch, it is currently in limp mode (restricted performance) It runs and drives fine just reduced power output.. The previous owner has already replaced the Timing chain and timing chain tensioner to try and fix the issue to no avail. The rover is currently sitting at my Indy shop waiting to be diagnosed, but they are extremely backed up and its taking ages.. The owner is currently asking about 50% of book value for it, if i don't just jump on it he already has others willing to buy it.. My question is What is/could be the absolute worst case to best case scenario and out of pocket expenses im looking at to fix this? should i just go ahead and jump on it before getting it diagnosed? Im worried i buy it and some freak thing is wrong and it ends up being a 10k fix im not sure as to what things cost on these rovers..

Thanks!