88 Chevy S-10 Blazer 4.3 wont run right

Ok on my truck I changed the timing chain and gears plugs wires cap and rotor about a two years ago. Ran great for about a year and a half then the problems started I have a random miss fire in park when in gear it wants to idle about 600-700 rpm so low the truck stalls out, and a strong smell of gas from exhaust. It got to the point where my truck wouldnt even start unless I had my foot on the gas I tought it was the iac valve so I unplugged it with no change. I unplugged the vacuum line that goes to the heat riser it will start up now with no gas needed but when I get off the high way turn it off then try to start it I have to give it gas again. Just changed the plugs and wires cap and rotor about maybe a month ago I started it while running looked at the injectors they seem to be squirting fine no leaks I also used sea foam please help im out of ideas oh and no check engine light is on