Problems After Another....

Ok i just fixed my heat shield for my car now all these problems are happening? Can someone tell me why when im driving with my lights my guage and my lights dim and when i step on the gas it shines back to full power? Also when im driving my gas sometimes goes down and then sometimes it would go back to a bar? Why does it do this? Also when im driving i hear these rattle sounds come from the passenger seat.. it only happens when i hit large dips, sometimes it happens when i drive over a a bump... whats wrong? Can anyone please help me?!?!?!

Well the gas would go up and down... like say im on full it would be full when im driving then sometimes it would go down one bar, then later on when im driving some more the bar would go back to the F.... whats wrong?

the lights dimming could be an alternator problem maybe....becuase when you give the car more gas the belts go faster giving more "juice" to your alternator....exmaple is if you have a big sound system and your at a competition and you see everyone reving there cars when they are testing....thats so they get the most amps out of there alternators....at idle some alternators put out like 80-110 amps and at max they put out anywhere from 140-170amps (aftermarket alternator i might add) ....in my car if i have the system up loud enough my lights and gauges will dim when i bass hits....as for the gas going up and down it could be from you taking turns. I know in my car if i take sharp turns my gas will either go up or down and or if im going up hill or down hill due to the placement of the sensor or fuel pump....in my car (honda accord) my passenger seat (the back rest) rattles/vibrates when i go over bumps n shit because no one is sitting in it to keep it still....or am i misunderstanding you there? those are my suggestions for what its worth

^ agreed

Ok UncleBen thanks for the tip, but with my gas even when i dont take sharp turns, its just when im drivin, in general it goes up and down, and with the rattle its coming from the right side of my car like near the engine.