Hyundai Excel X3 bad idle when aircon on.

Hyundai Excel X3 (1995) idle drops dramatically when aircon compressor turns on and is slow to recover. Normal idle is (now after work below)
fine. What sensors (if any) control or can effect this? Have just had an on car injector clean done to fix rough idle (low) all the time, the mechanic also mention the idle air flow sensor area was carboned up and he cleaned - the problem only occurred after this, idle went up previously with aircon. Any thoughts? Also can any provide a link to a service manual, I can only find one for a 1991 model which is not the same.
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