Car not running right, need help!
Car not running right, need help! Ok, heres the situation, I got my car back from the transmission shop yesterday. It ran great, shifted hard, and just drove awesome. Now, since I had something to do when I got it back, my dad went and picked up my car from Amco for me. One the way home, he filled it up with 89, a full tank. I drove it when he brought it home, not knowing it was filled up with regular. When i drove it, i kind of laughed to myself thinking, wow, its kinda sluggish. So i called up my dad, and sure enough, he told me what he did, i was a little dissappointed, but I decided, hell, I'll put a little octane booster in it, and give it a little kick in the pants. So I put a bottle of NX octane booster into my full tank, and it ran awesome, just so much more throttle response and speed. 
. Now, this morning, when I started it up to go somewhere, it idled around 4-500 and it stalled and sputtered, and would just die. It ran like complete ****. So I dropped it off at my local GM dealer for them to look at it, and now i'm sitting here, wondering what could have caused it to run like that? The gas? Something else? I'm stuck
. Now, this morning, when I started it up to go somewhere, it idled around 4-500 and it stalled and sputtered, and would just die. It ran like complete ****. So I dropped it off at my local GM dealer for them to look at it, and now i'm sitting here, wondering what could have caused it to run like that? The gas? Something else? I'm stuck update: i just ran to the dealer, I tried starting her up, she wouldn't start. Fuel pressure was kinda high, not too high, but more than normal. I finally got her started after I gave it some gas, but I had to hold the gas above 1000rpm to keep her running, when I let go of the gas, she'd die. Any suggestions? 
