doesn't start on hot days

[man.united332]

Hi Guys,
my first experience with Golf 2008 S, bought it from friend, i am having some issues , please help. thanks in advance.
1. initially the pickup was very poor, changed one of the coil and pickup is much better.
2. on hot days it can take upto 15-30 min to start, cold start is fine.
3. one of the spark plug tip gets black, mechanic said its the petrol gathering on the plug, not sure the reason.
4. engine doesnt get power while driving in 5th gear around 60mph and doesnt goto 70 easily unless i switch to fourth gear.

Thanks for your advise.

[Teutonic_Tamer]

You really need to get it scanned by someone with VCDS.

However, you can do certain checks yourself.  Make sure it has the correct spark plugs, as they are very sensitive to this issue.  If in doubt, replace them with genuine OEM from TPS.  Check the air filter element - whilst no-one expects them to be pristine, they should not have any clogging with dead bugs, sand, straw, etc.  Also check the air intake system is totally clear - no birds nests or dead rodents!