Hi guys,
. Just got this car. 3.8, 109,000. Previous owner said it wont go over 20 mph, which it doesnt, I tried. Before I get crazy on this I figured I'd ask for some direction first. Where should I start?? I am picking up a fuel pressure gauge today after work. Also, I have no check engine lights.
I am replacing the BCM also as I have a mystery battery drain. Thank in advance

 

First place I would check is the catalyst convertor. Does the exhaust sound weird like it restrictive ? Can put your hand over the tailpipe and see if there is normal flow when you rev the engine. Good luck

 

I'll add, can you look under the car, does the cat get red in color?