My 2003 Z sounds and performs excellent in 1st and 2nd, but in 3rd and 4th the car feels super sluggish and has a gargling sound that is thicker sounding than other gears. In addition, when it idles it feels like I have aftermarket cams. It sounds so darn horrible and clunky (at idle) but idles exactly at 650 and is unwavering.

I did some searching on the forums because I thought it could be related to my MAF or popcharger, but I can't find any concrete evidence against them from other people's problems. I also had a burned out coilpack last month and when i was in 3rd and 4th id throw misfires like crazy. I havent thrown one since I replaced the pack but it is still as sluggish as it was right before a misfire.

I was thinking it also might be the summer heat, although I wont know for sure till winter comes around.

 

Have you had a scan tool connected to it?