1985 Hyundai Pony Lousy performance?

This vehicle has 156,000 kilometers and is a 1985. Single owner very well maintained before I bought it. I've had it two months. In that time I've replaced the spark plugs with the ones recommended in the manual. Wires are good from the last set of plugs (very good shape) distributor and point are all good too. This vehicle has the 1.4 L I4 with a 5 speed manual driving the rear wheels. It is carburated with a manual choke. Recently I've been having toruble during cranking to get her to turn over and even after warm power has been very poor. Particularly on hills. Idle seems lower but is not uneven, however the first immediate moment after pressing the gas the engine shudders a bit then is fine except that it feels like I'm towing a whole nother car behind me. Holding highway speed requires almost 3/4 throttle and it slows down on hills. I pulled the plugs today and they were a bit dirty so I cleaned them with no change. Noticed one of the hoses had popped off what the manual describes as the EGR. Put it back on but with no change. I have not checked the fuel filter. Other symptom. There occasionally is a popping sound and the engine will stumble but then recover. This sound is not eminating from the exhaust but rather seems to be happening just above the carb. I think it's blowing backwards into the air filter housing. It's not violently in fact compared to an exhaust backfire I could only describe as a very soft poot. There are no mechanical clangs or bangs and aside from the occasional poot and lack of power everything SEEMS fine. This is happened over several different tanks of fuel of different grades from different stations. Also my fuel economy has dropped by nearly half. That's all the symptoms I've noticed so far. Please assist I need to take a road trip on tuesday to see relatives for xmas. I fear I wont be able to get her up the backroads.