93 Alty Problem?

My friend has a 93 Alty.. the Ka24 dohc motor... Tonight we were sittin in a parking lot and it all of the sudden almost "stuttering" and sounded like it was missing even though its not...the plugs and wires are all fine... He also has a cone filter with adaptor onto the mass air flow...and when he rev's up it sounds like its sucking in way too much air or trying way too hard because it doesnt sound at all like it used to

It is taking a very long time to start (if it does) and it doesnt do much when rev'd or driven some, only at idle.... It will also die after a little bit of time sometimes but sometimes not... We asked a few people and came up with bad gas or something wrong with TPS Sensor? Can you guys give me some input?

It is possibly a intake air leak.