Machanics have found this habit of repairing the tapets of cultus saying that they are jamed and are unable to adjust automaticly. Some three machanics have recomended me this and they charge around 3800. But I have not gone for this.
Just have complete tuning, plugs, wires, air filter and timing checked.
The problem you are facing is Decrease of RPM even the engine is hot. It does happen after tuning, Just increase the RPM from the kit or adjust mixture. Your problem is not big.