Please please can you help me

Please please can you help me. I have a 98 toyota harrier with the 3.0 ltr v6 petrol engine. It started giving trouble a few weeks ago. The symptoms come and go as they please. One minute the car is running, idling and performing great and the next minute the engine starts to lose power. It starts idling very rough (like a misfire) and there is a sucking sound coming from the air inlet side. When the engine is doing this I have almost no brakes and very poor take off power. When I put the aircon on or put it into drive it worsens.

i will be driving quite fine and all of a sudden no brakes. I pull off and the engine is running really rough and making the sucking sound. Sometimes over night it somehow corrects itself and will be fine for a few days until it starts again. The engine light has come on twice but only briefly.

i have so far changed the spark plugs, fuel filter, airflow sensor, air filter and have had the throttle body cleaned. I suspect it has something to do with vacuum.

i live in kariba zimbabwe and am wondering if it isnt the catalitic converter or something.

please help asap

how do I make a donation from zimbabwe. My mother lives in the uk so maybe can make a plan