manifold leak?

Have 94 full size blazer 212,000 mls. keep hearing a "ticking" noise when driving. engine chugs and surges a little when going 20-40mph. also garage has a gas smell after I shut off truck. Could it be a manifold leak.

if it feels alittle sluggish when excelatering it could be a mountain of things, but if you are in your garage and you smell "dirty" exhaust check under the hood and listen for a puff. it wont be real loud but it will sound out of the ordinary. also if you are in an area that is still kinda cold you can start you vehicle out side and you could tell if you have an exahust leak. I had the same thing and i found a leak off the manifold going to the pipe. all i had to do was thighten the bolt so the donut would seal. but then again i could be way out of wack. also check your feul injectors could be clogged an your not getting enough feul in. just a suggestion is all.