I don't know what would cause the smell of gas, but my Blazer was running rough and backfiring so I did all the same things you did, as well as replace the feul pump, and it cleared it up. Don't know if it'll help but it fixed mine.

 

Did you ever resolve this problem, I have the exact same symptoms with mine.

 

Mine turned out to be a defective electronic ignition module (the little box next to the ignition coil on top of the motor). The car got progressively worse (sometimes starting and running fine, sometimes starting and running rough/backfiring, and sometimes not starting at all). I replaced it about 2 years ago and this problem hasn't returned.

 

Thanks for the up-date.

As for Performance Improvements, the X & W code engines should Perform about the same however, if your engine wasn't running right to start with, it would obviously be a significant improvement.

I've heard a lot about how the NEW STYLE spider increases HP and Torque but in reality, the specs are basically the same, just a different design.

I'm not a specialist or expert with these things by any means but I have researched them quite extensively and I have found no factual data suggesting added HP or Torque.

I'm going to be up-grading my engine with these in the near future simply to eliminate future problems, so Thanks for the link to Amazon,, best price yet.

Keep us posted,, We're all in a learning process here and appreciate all the help we can get.

 

Could I ask for Specific Details of how you engine ran "at idle" and "off idle"?

I'm having issues with mine and I just can't figure it out.
It has a bad hesitation or throttle response and it will backfire if I give it 3/4 or full throttle from idle. The Coil is one of the Very Few things I have not replaced and I am getting NO Check Engine Light and NO CODES

Thanks in advance,