i picked up my sammy while living in denver and had the same issue. i hated using freeways. it was just as easy to take backroads. got there just as fast.
does it run rich (a.k.a. fuel smell from exhaust)? the altitude does play hell on the fuel system. the carb is a pain to tune because there is no air fuel mixture screws other than the idle speed / idle fuel mix screws. it wont do any good if you mess with them though. trust me.
here ill get specific for everyone.
try not shifting until 5000 rpm. 4000 first gear 5000 the rest. dont be too afraid to push it. the engine can take it. do replace the timing belt soon though. takes 45 minutes. its cake walk.
check your timing. you may have to play around with it just a little bit. try it at base timing (10 degrees before top dead center) and then try advancing or retarding it just a hair and then driving it. do it a few times until you like it. i went to school there for automotive and had a shop to work in so i lucked out. if you want a shop to take care of it, go to Westwood College-Denver-North
7350 Broadway (i25 & us36) behind the totota dealership. pull up to the shop doors (north west side of building) ask for alan,joe or greg. it wont cost you anything to go there except for parts. free labor!
another thing you need to check is your catalitic conveter. smack it with your fist a few times (when its cold). if it rattles replace it, or take it off and gutt it out. of course its your ticket.
check the vaccume advance syloniod (side of distributor). follow the hose to the side of the carb, disconnect it, suck on it then plug it with your tounge and watch the sylonoid for a few seconds. it should pull in and stay until you unplug the hose. if it doesnt, replace it. check the hose for leaks first before replacing the sylonoid.
check the egr sylonoid the same way (below the carb attached to the intake). also remove it and clean the carbon out of it realy good with throttle body cleaner. buy a new gasket before you take it off though. "egr gasket"
make sure all of the vaccume lines are tight. if they slide off easy, they leak.
heres a funny one check the high altitude sensor ive never quite been able to grasp the idea but heres what alldata says.
("Disconnect compensator electrical connector and connect ohmmeter to compensator.
Check that compensator is on at altitudes above 4,000 ft. (1220 m) or off at altitudes below.
Reconnect connector.") ( i guess you need to mail it)
car quest carries the carb kit for like 30 bucks if you want to attempt rebuilding the carb yourself.
there are two little switches on the front side of the carburetor that tell the pcm when its full throttle or full closed that should be tested also. they should be 0 ohms. 0.5ohms is getting bad but still ok. youd like to see 0.4 or below. if you need replacements i found some on ebay that will work with a little modification. the switches match perfectly other than they have a little spring loaded roller arm that will need to be cut off. (search for "weather resistant micro switch") on ebay to find them. costs like 4.00 each. youll have to modify the wiring also. (need 4 spade connectors) just cut off the old switch and connect the wires to the new switch. 1 switch at a time. dont mix them up. the wires can go on either terminal of the switch, but the switches cant be mixed up. its all ive been able to find that will work. they are hard to find.
sorry if im being too exact as if youre a moron or something. i figure others will be reading this so i thought id be accurate so it can help the ones who dont quite get it.
and yes phloop is right also you need to test the float bowl vent sylonoid. id send you a pic but i cant so heres what i can give ya.per alldata
Disconnect canister hose from bowl vent nozzle of the storage canister and connect new hose to pipe leading to solenoid.
Blow air into test hose with ignition switch in both on and off positions. Air should pass through hose in both tests.
Start engine and allow to idle, then blow air through test hose. Air should not pass through solenoid.
If SVS fails to perform as outlined, check feed circuits from ECM and ignition switch and repair as needed. If feed circuits are satisfactory, SVS is defective.
Remove test hose and reconnect original hose to canister.
there are a ton of aftermarket upgrades you can do to get better perforance too, but im pretty sure you know how to use google. this is just what i can think of to do on a budget to get a little more power oou of a stock zuk. i was able to pull off 65-75 unless i was headed up hill with mine stock. never have passed anyone who wasnt broken down on the side of the road though.
