I took my blazer to a shop and they did the manifold intake gasget set replacement. He didnt change the oil right away, i just changed it today a week later. I noticed a type of ticking when i reved the engine to 2k rpm in park and when im driving it will make the noise right before it shift gears. What is the issue, i checked youtube and it sounds just like the balancing shaft, how expensive is this repair, is it the mechanics fault or just a coincidence? please help, i do not have thousands of dollars to put into this engine.