My RR loves its little 650DP. I have a 750 DP as well but the car doesnt run near as well. Major bogs, hesitation, sputtering, etc. Both carbs were rebuilt by the same guy at the same time. Both were put back to Holley specs with the proper jets. I took the 750 back a second time to have him go thru it again with the guy even driving it with the 750 installed. For some reason my car just likes the 650. Either that, or there's something wrong with the 750 that hasnt been caught yet. My car has headers, mild cam and head work (906's), 4 speed. Who knows.