hey mate I had a very simular problem with my car aswell high rpm it was breaking down but still pulling!
I had NGK V power plugs and the thread was a few mm shorter then standard NGK plugs which coursed the spark to be futher away from the pistons and the spark was getting lost! I changed them to standard plugs and solved the problem revs out super clean.
This mite not be the issue with your car but its worth a try, cause I 1st thought it was my coils so I went out and brought new splitfires ($500) which I eventually found out it wasnt the problem it was a set of $16 plugs