How about you are sedning it out for a custom tune.
Could you have them add something for looks.. like a Duck Tail spoiler, new Hood, Grill?
How about some electronics... have an I-pod adapter or satellite radio added in. How about a Sub in the trunk?
All these are much cheapper and easily noticeable by her.
Though seriously, you and you wife should be on the same page on what you want. My wife and I worked out a plan for our money. Since we are still young and have not purchased our own house yet (many reaosons why) we devised a plane to get there. I can have whatever I want for the Mustang, as long as I put 50% of the cost into the savings account for the House Down Payment. So, like I want Kooks Long Tubes, so last night I moved $700 over into the savings account. Now the next time I free up $1400... I can get long tubes.
My wife likes shoes... all she has to do is put 50% over into the savings whenever she buys a pair. That keeps us both happy. Plus I handle all the money amd since she gets paid once a month, I just take her pay check, devide it up by percentage based off our incomes and pay the "us" bills. Once that is done, I transfer the remaining money over to her account and ask no further questions.
We never fight over money this way, and when major purchases come around (like long tubes) we discuss it. Sometimes I have to wait a month or two before getting somethign for my cars... other times she just simply sayes if we can afford it.. go ahed.
Maybe if you try talking to your new wife maybe you can work these thing out before it tears up your second marraige. Money is the #1 cause for divorce (#2 is cheating). I can tell by the way you made some of your statements that you two have some grief between the two of you on what the money should be spent on.
BTW, I am not endorsing using any of the above mentioned Items on your wife to hide the car for a few days