I had installed a 770cfm truck avenger on my 454ci in my 77 K10 and it did'nt work very well ( low speed bog ). After talking to Holley they said I needed a 670cfm on the mostly stock 454. So I sent them my 770cfm and they replaced it with a new 670cfm. Installed it Friday afternoon and it works perfectly!! I did'nt even have to adjust the float level! I have to get a vac. gauge from a friend to check the idle mixture but right now it is running great!! Hopefully this week I will have the time to get it on some hills to see what it is capable of. Thanks to everyone who replied to my other thread for the help.