2004 Pontiac Bonneville SE

Engine size = 3.8L V6.
Repairs: Front motor mount changed, all motor mounts were loosened and then tightened. Spark plugs have been changed, platinum plugs were put in.
Question = I have a vibration from my motor, I feel it mostly when I am stopped at a red light or stop sign. I can feel the vibration in the seats, the steering wheel, the brake pedal, right through the whole car. It's like I am in a big truck.

This started after the repairs were done that are listed above in "list any repairs". Before this it was smooth, I could hardly tell the engine was running. The dealership tells me that this is acceptable and there is nothing they can do. But, to me if it was smooth before, it should be smooth after the changes.
Is there anything I can look at or do to see what could be the problem?

Answer: Well, either something was forgotten about and left loose, or from what you describe you may have a misfire on one or more cylinders. Since spark plugs were installed, I'd check to make sure the ignition wires are attached properly and in the correct firing order. You may want to pull out the spark plugs and check if the gap has closed on any or the ceramic could be cracked. This would usually set a check engine light if there is a misfire, and you don't seem to mention that. If all the motor mounts/trans mounts/subframe bolts are tight and the mounts look in good condition, you might also want to check the harmonic balancer. When these go bad, they cause a vibration but are also usually noisy.

I Can Smell Gas

2005 Pontiac Pursuit.
Question: there are times when you get out of the car and you smell gas. there is no gas on the ground no leak.

Answer: If you are smelling gas, then there is a leak somewhere. Gas evaporates very quickly. You need to get it to a mechanic ASAP to find the leak. If it is in the engine compartment, then this is a fire hazard. Some areas to focus on would be the lines, fuel pressure regulator, fuel injectors and injector O rings.