Hey ferm help

[Skools Out]

my 99 tahoe has a misfire / skip on the highway usually after getting into the throttle when i let off and it goes back to OD if i ease in the throttle it tends to skip sometimes, if i let off and get back on the throttle it's gone. i put new plugs AC Delco and it has about 25k on the current plug wires and i had AC Delco cap and button replaced 25k ago so i tried by replacing the cap and button with aftermarket Sat. only due to no one had AC in stock. it ran smoother but now a check engine light with multi misfire code. i'm going to take the Advance cap and button back and get a new AC cap ordered or would you go with the aftermarket with the brass inserts? any other ideas on this skip. the tahoe has 150k on it. i have a bad feeling it's the stock original spider that is in it. what ya think?

here's a link to the type cap i was questions on

http://cgi.ebay.com/ebaymotors/GM-Vo...item4cf68a5956




Ferm would i be best off to just go ahead and change to spider to one of these and be done with it? is this a tough switch out?

http://cgi.ebay.com/ebaymotors/Delph...item27babaecca