Which one is better? HIgh SAT/ACT test scores and low GPA or High GPA with Low scores?

<p>I just got my ACT scores in this morning, 31 composite ( 35 math 30 reading 28 english 29 Science)
Unlike others, I have a very low GPA (3.5 unweighted). I've checked the colleges that I want to go to and many of them accepted students with SAT scores range from 1700 to 1900 (ACT 26-29) and 3.8+ GPA. but people with high SAT/ACT scores and low GPA (my case) tend to get rejected or waitlisted.</p>

<p>thats not a good news for me, how can colleges turn down people with high SAT scores but low GPA?
In my opinion the standardized tests score should be more convincing as to whether the student will excel in college or not than GPA, since GPAs are generally inflated in many schools , that was not an excuse for my poor GPA, I'm just wondering.</p>

<p>btw I really want to go to UMichigan's school of Engineer, I have taken 2 SATs already and planning to take a third one next month ( highest score so far is 1900, i'm confident to score above 2050 on the next one or even 2100) my ACT is 31 composite, current GPA is 3.4 ( will be higher after my first senior semester) taking the SAT subject Math II next month as well, it will be 750+. By the way, my curriculum is fuked up, I have only taken two AP tests so far( 5, and a 3) classes taken in high school were not challenging at all, all due to my low GPA because my school only lets people with 3.8+ GPA take AP classes.
How should I persuade UMichigan to accept me while I have a low GPA? if the key is the essay, how should I write it?</p>

<p>Thank you for finish reading my post, any advice would be much appreciated!</p>