Just keep upgrading your engine man. It will take awhile because how expensive the parts are. Take your time though and make sure you never pink your campaign car. Pinking your campaign car would be a costly mistake.
Also, if I may add, try to farm perfect shifts with your highest class car. It will pay more per shift. If you do decide to start pinking, a good place to do it would be during turfs. Atleast you have security in knowing that everyone is in your same lobby.
I was actually thinking about getting this car also. I noticed this car was the same rating as the MP4 but had better stats as you mentioned. I'm surprised it is not quicker than the MP4 or ZR1 since it cost more gems than the ZR1.