Fifth and fourth gear lagging problems

Hello, I have a '90 Intruder 750 and am having issues with lagging in fourth and fifth gear at high speeds; especially with wind or inclines. This feels like a jetting problem that I am not getting the correct air to fuel mixture. I am also experiencing poor gas mileage not to mention reduced top speed. Any help is appreciated. 
-J

Hi jason do you have the stock gearining on still ?

Hmmm.... sounds like shes running too rich Jason. Take her in for a tune up. Best performance is on the lean edge. Back her up to a fence or wall and give it a rev or two... does it leave sooty marks? if so, too much fuel.

if its running that rich you will smell it if you stand at the back of the bike
just starting with the basic start list to find problem when did it last have a new air filter and plugs do you use the choke when starting it when you push the choke back in does it go back in proper (cable) is your tank clean inside (no rust) has a bit of crap got in the carbs or may of bin a bit of shity petrol have a go with silkylene (not sure if thats spelt right) used it on my bike great stuff you put some in your tank top up tank with petrol then ride it till you need to fill up go's through your carbs cleens them runs through the engine cleening and coating bits worked a treet on my bike use once go through a few tanks of petrol then do it again but dont use it more than that just good to in small doses twice should be enough but not twice in a row when i get back home (friday)i'll put the proper name up you so can check it out

Thanks for the feedback. It does seem like it is running too rich. I have the day off Sunday and will be peaking into the situation using the comments. I will get back with you all with what I find, thanks!