I'm really having hard time determining whether a verb/s should be present perfect or simple past. Canonical Post #2: What is the perfect, and how should I use it? answer provided by StoneyB in this post was useful and at the same time it made me more confused. It says the present perfect tense has three uses continuative, existential, and resultative, but couldn't all past tense be categorized into one of this, thus making it present perfect?
For example, I found five errors using the information you have given us. Couldn't found be categorized into existential, thus, I have found five errors using the information you have given us.