AGI stands for Adjusted Gross Income. If you file a regular 1040 then this will be line 36 on your return. It is before exemptions and standard/itemized deductions. 401k and 457 contributions lower your AGI so those help keep this down. After you take your exemptions and deductions you get to TI (Taxable Income).
On that Itemized Deductions phaseout, if your AGI exceeds $142,700 then you begin to lose some of your itemized deductions. Basically, you lose 3% of AGI over $142,700 up to a total of 80%. For example, if your AGI was equal to $152,700 then it would exceed the threshold by $10,000. $10k times 3% is $300. So you'd lose $300 of your total itemized deductions. So if you made a huge sum of money and your AGI was several hundred thousand, you'd loose a huge chunk, but never more than 80% total.
Ok, anyone still following me?
Also for the IRA, do you have a Roth IRA or a traditional? Just curious because they have some very different features to them. Also, if you are unsure if your income will be too high to contribute, remember that you have until April 15 of 2006 to make your contribution for 2005. You just have to indicate what tax year it is for. I personally make my contributions in February or March for the previous year after I file my tax return.
Hope this helps. If not, keep firing questions at me and I'll keep explaining until it makes sense or you go postal.
Oh and Molina, what this is all about is job security. The more difficult and convoluted it becomes, the less people want to deal with it and the more valuable someone like me becomes.