Need Urgent Help Plsssss

[Makdubails400]

Hiii experts pls help i just now made registration on this forum to get help , i have ls400 us specs i li e in uae . I m gonna tell u exactly what happened with car , few days back i noti ed that my car rpm went very low around 300 rpm to 400 rpm i ignored it n was driving usual but then 1 more problem came tht wen i turn on the ac then cars rpm keeps fluctuating up n down n ac also seems like its tripping in n off it was becoz the rpm was low n car cudnt take the load of ac. Then i took tht to a local garrage n tht the worst thing happened , tht monkey mechanic started experience on my car , 1st he removed the pressure switch from the ac compressor n replaced with tge other 1 which was also used , because of tht now i m facing low cooling before my ac was like an ice maker really , 2nd thing he did he adjusted the speed rpm by hand which is located with the engine there u can see the wire also of the speed , for the time bieng rpm went high but wen i was driving the car i feeling the drive very unusaul n uncomfortable , then reached home n switched of engine n restarted again then it was all worst , my rpm went upto 3000 n car was just in park in nuetral , then i loosen the wire which he did tight from hand n rpm came low upto 1 k . Now its few days car rpm is very unstable n now cars heating needle also stay lil higher then before n ac also works very slow + fuel consuption is alsi very bad , plssss guys help me this car was very silent comfortable while driving n there no heating issues at all . Kondly help me wht can i do now now is noisy also. Pls pls ur advices n suggestions Ls400 1998 model us specs

[Makdubails400]

My 1 more request if anybody from dubai / uae here pls guide me the good garrage or mechanic for lexus ,, thnks guys