I will again try posting your answers.
I was running into some kind of error message when posting, so, lets try this again.
A - Trouble upshifting is often caused by too much oil in the transmission (I used 10w30 in my bullet, and the Targa's no doubt the same, in that.)
There is, or should be, a large screw on the left side of the transmission exterior with a paper washer - this is used to check the level of fluid in the trans - check it, if it starts pouring out (not dripping) you may well have too much fluid in there.
Or you could just change it, with 10w30, and the correct amount - usually 300-500ml.
B - Change out the plug, to a Champion Platinum, old reference # J82C.
C - Clean the choke lever assembly with carb cleaner, it's usually located on the left side of the carb, if it's a DelLorto.
D - Liquid is bad, yeah, but almost as bad is 'venting' from an improper cylinder seal (why they use a metal-to-metal no-gasket seal of two pieces of different kinds of metal is beyond me...)
It should be fairly obvious if it is, simply clean the cylinder thoroughly and look for signs of venting.
E - Actually, having a full exhaust on there helps assist compression by something called 'back pressure' and ensures better running.
with the old exhausts, you could pull the baffle (the piece on the inside) for a little better performance at the cost of a slightly different exhaust note...but i thought it sounded neat, myself.
Better still, however, to go with the Bi-Turbo, it makes more difference and is more effective.
Note: On exhaust silencing - I did see someone take the baffle out of one of the old exhausts, drill 4 strings of 8 1/8" holes in it, pack it with fibreglass, and put it back in there.
It did not significantly degrade performance, and that bike was nearly silent in low 2nd gear.
F - The only decent and trustworthy sprocket mod would not help too much, and is of medium difficulty even for the experienced to install - but it is fairly inexpensive, so make your own call there.
G - Tomos bikes generally run well on anything, but using the highest grade gasoline would prevent hassle in the long run - try sunoco's ultra 94.
H - As I recall, the oil mix for that engine is 50:1, as long as the injector is functioning, I wouldn't bother pre-mixing, have tried other ratios with that engine and it generally doesn't help.
You might add a teaspoon of octane booster to the oil when you fill it, just don't add too much.
I - Doing a brake job on a 'ped is a bitch, for a novice...actually most used bikes you get, need one, a lot of the time that is the factor that convinces someone to sell them - the hassle of doing a full front&back brake drum replacement.
Most kids who buy them, keep using the adjustment screws till they don't work anymore, usually jamming them...then sell the bike.
So yes, replace the shoes, front and back, and plan on it taking all day long.
J - I've never had a speedo on a 'ped actually STAY working for any length of time, don't bother replacing it..not like you need it, really.
K - Tire PSI, i've always used 32, but anywhere between 28-35 has been done, for various reasons of weight, weather and performance.
HIGHLY reccomended are Cheng-Shin interrupt-tread tires - they stick to the road and work well on dry pavement or even the worst of weather.
(would that they made tires that good for cars!)
L - It's been done, but much easier is just bungee-wrapping a boombox to the cargo rack.
May you only meet the road with your wheels between you,