I have an 04 with eco that now has 105,000 miles. My only mod is a turbo muffler that gave me a mile or 2 more speed in the quarter mile. ( I have an area marked on the highway that is marked a quarter mile) my car seemed to get a little faster as the engine put on the miles. today I changed the plugs for the first time. they are now using iridium instead of platinum. I instantly notice an improverment in smoothness. I took her out in 33 degree weather and hit 90 mph.( the best yet) I have used mobil one since the car was new, but recently started changing it every 10,000 miles
because my miles are 90 percent highway and they say the new
extended performance oil is good for 15,000 miles. I think this engine will be good for 500,000 miles. I think my next mod will be the supercharger. Are people having good luck with the Gm supercharger? How much is it installed at the dealer? my LT-1 caprice wagon (149,000 miles) with dynomax turbo muffllers did 93 mph in the same area today
. No other mods on the wagon.

yes i'm having good luck with mine and i did the install,most shops will charge you their regular labor rate and however long it takes them to do it,so if it takes them 10 hours and at 60 bucks an hour,well you do the math,after spending 25hundred on a supercharger,set aside another thousand just to be safe ,or you could do it take it to the dealer and have them reflash it for less than a hundred bucks,if you don't flat bed it or live really close,drive it slow and with caution,if you have futher questions please ask


if at first you don't succeed,you should probably give up