I need a tongue lashing from a good MTT player

[Bigwig]

First, some quick background on myself. The vast majority of my play is STT's. I've amassed excellent ROI's over statistically significant sample sizes at both $30 and $50 (30% & 25% respectively). I say this only to make clear that I certainly 'know' what I'm doing, but I've reached a point in my MTT career that I have to admit something:

I suck at MTT's. Wow, that feel's better.

In order to make good money in MTT's, you must make final tables. That's clear. To make these tables you must build a stack at some point. In STT's, I simply play tight early, and often double up when I hit a BIG hand like trips. Otherwise, I'm pretty much folding a lot and rarely preflop raising. This is correct strategy. But it's clearly not in MTT's, where I consistently survive longer than the average player in the field, but rarely with a top notch stack.

So, my question: What general strategy changes do I need to make in order to be able to get better at MTT's?

Thanks in advance.