I researched a lot when I was buying one. I had 4.4i before and then after selling it, I was in the same dilemma whether to go for 4.6 or 4.8. I read tons of reviews and spoke to my friends having these and test drove these and finally concluded with 4.8i. I am glad I made this decision and have no regrets and enjoy my ride everyday. Even the growl of 4.8 makes me happy.... Rest are all personal preferences. I'll suggest to test drive both and make your own decision. The only issue with 4.8i is front air suspension but just keep $700 aside and you should be all set.

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2005-4.8is