A few things...

It sounds like you're in excellent shape, save one item- you're not trading technology. The AI will trade technology around, and thus end up outpacing you easily if you stay research-isolated. If you get involved in the technology trading, your research opponents are equal in number to the number of major and minor races in the game. If you shy away, your research opponent is all other races combined, and though none may be a match for you individually, their combined might is able to easily outpace you.

The solution is simple: be the technology broker. Grab those technologies while you still have some of your own to exchange, then ship them around for more technology. If there's no new technology, then squeeze them for extra money.

~SDC~

To become the tech leader you need a diplo bonus. I always choose it in the start options. Tech boni are irrelevant, I try to get starbases on those ressources later.

At the beginning I'm very bussy with colonizing. I don't research anything.

When I got some free ressources I only research Communication and Universal Translator.

When all the colony ships are on the way I look through all AIs (including minors) and make a list off all techs they have.

Then I research a tech noone has. Usually it is possible in one turn. I try to get diplo enhancers in the first round (i.e. Diplomacy) from the minors.

In the second turn (don't save and reload, the AI which got your tech would trade it) I research a second tech and start trading with everyone (again minors first). Start with monopolies, i.e. techs only one AI has. It might take two or three passes but I usually get all techs the AI has (more than a dozen for my two techs with the exception of some military techs.

Then I stop researching again until the AI leads too much, gets a critical tech (for wonders, trade goods etc.) or I need more techs.

I do this two or three times a game until I lead. From that point on I stop tranding techs and research everything by my own.

I find a good economy really helps. With +50% economy (Resources + Party Perk), the 40% you spend in research might equal three times of the other empire's 60% or more. If an empire with normal economy, they can only spend so much, even if they crank the research option to be 90% of their spending.

~SDC~

Correct me if I'm wrong, but doesn't economy only affect your plantary income? It's never made much of a difference to me, especially once you hit that 4xPQ barrier when considerable economic bonuses only budge income up by one or two. On the other hand, more economics should let you set a much lower tax rate with minimal income impact, leading to higher moral, population growth, and ultimately more production capacity.

Trade, on the other hand, doesn't suffer from such limits. I routinely end with trade income six times higher than my tax income or more, allowing for the same tax break bonuses while letting me use alternative political parties and starting bonuses. However, diplomacy is where the real gold seems to lie early on- a nice boost there, combined with careful management of tech trades, can keep you just about on par with the majors in technology. Plus, you can bribe the majors into attacking each other fairly easily- do a lot of that. If done right, you can keep the Relations screen a mess of tangled red lines, except for those five orange lines all heading your way Just try to keep the fights oriented such that it's an endless quagmire, as you don't want any of your trading partners to get blown away too quickly. It's fun being the Illumanati.

Once the initial 'flurry' of things to build dies off, I crank research up and sail away from the pack- with a considerably more developed planet set thanks to massive social production instead of research and warfare, I can hit TerraComputers pretty quickly and then storm through the research branch, racking up the additional research bonuses and trade goods while the others waste time on the capital ships branch.