Aside from staying away from hack mechanics, You need to do 3 things asap.
1: TUNE ECU (android phone with proper cable)
this will help you diagnose the TPMS (throttle position sensor), there are 2 of them, one on the secondaries butterflies and the other on the lower primary throttle. You can easily test them with TUNE ecu. They can be swapped around but its a special trick as they both spin in different directions.
2: lever up the fuel tank and check the 3 coils for the 6 spark plugs. There is a high chance all you need to do is "crimp" tighten the connection of the spade connections to the coils. this is a very common problem. Also those coils are old school stuff. There can be hair line cracks in them that tighten up when they get hot, this can also be the issue. You can swap them all out for an overhead coil setup that is bullet proof. While you are at it, check the spark plugs visually. This is probably what your problem is.
3: Check your ground connections, very known for being terrible, the ECU likes to have a specific voltage, and this is a very quick and necessary fix for many other issues.
Aside from this i would drain the fuel and put in known GOOD FUEL
When you have Tune Ecu, you also should sync the throttle bodies, due every 10K miles. There is also a valve adjustment you need to do every 10K miles as well.
here is a link to the coil fix, i did this and it turned my perfectly running 06 into an even smoother running monster that is guaranteed to never have a spark problem i cant fix supper cheap and fast.
get 2 of these
Amazon.com
and a set of these
Amazon.com
Solder and shrink wrap the new connections. easy peasy.
Here is a video someone else did that can help, i tried to find the coils he got in the video but they are $$$$$, because they are SO EASY to swap out and test the Ohms on, just go with these aftermarkets.
