2003 Chevy S-10 Noise after replace the Intake manifold Gas

Hi,
Last week I took my 2003 Chevy S10 4x4 ZR5 4.3 litres to Canadian tire to change 1 head light. They made a visual inspection on my pick up and they recommended me to change the Intake Manifold Gasket and the water pump (was leaking) and they made me an estimate. I purchased the parts there and went to a local mechanic shop (here in Edmonton, AB) to do the job. Now my car has a constant noise, but I only can be hear inside the car, it is more intense in front of the drivers seat, like a continuos bee flying but when I push the gas I cannot hear it. I cannot hear the noise outside the car.. I took the pick up back to the shop and told them that my car didn't have any kind of noise before, but they do not want to do nothing else about that. What could be the problem? Where should I take my pick up to have it fix. Thank you!