no self rpm drops function

my 4 runner is 94 V6 3VZ-E with 258000 km, when I first start my car the RPM's around 1450. But after minute no RPM drops just heard noise little less, until drove over 7 to 8 minutes distance, RPM feels less drop back to normal, is it the fuel cut RPM function inop? On last year before, I replaced new throttle vlv, problem still remains?
Any advice would be appreciated, Thanks.